Which organ is primarily responsible for filtering waste products from the blood and producing urine?

Correct answer: Kidney. The kidneys filter nitrogen-rich waste and excess water from the blood and excrete them as urine. Each kidney contains roughly a million nephrons that do this filtering work. The liver also processes blood, but its job is detoxifying chemicals, breaking down old red cells, and metabolizing nutrients into bile and proteins, not making urine. The pancreas produces digestive enzymes and the hormone insulin. The spleen filters old red blood cells and stores immune cells but does not produce urine. Urine production is the kidney's defining function.

Water (H₂O) is best classified as which of the following?

Correct answer: A compound. A compound is two or more different elements chemically bonded in a fixed ratio, which is exactly what H₂O is: hydrogen and oxygen locked at 2 to 1 by covalent bonds. An element contains only one kind of atom, so water cannot qualify because it holds two. A mixture is a physical blend whose components keep their own identities and can be separated by physical means, like salt water or air, but the H and O in water cannot be separated that way. An isotope describes versions of one element with different neutron counts, not a multi-element substance.

Which layer of Earth's atmosphere contains the ozone layer that absorbs most of the sun's ultraviolet radiation?

Correct answer: Stratosphere. The stratosphere sits roughly 10 to 50 kilometers above the surface, and within it the ozone layer absorbs most incoming UV radiation. The troposphere is the bottom layer where weather happens and airliners cruise; it lacks the ozone concentration. The mesosphere is above the stratosphere and is where meteors burn up. The thermosphere is higher still and hosts auroras and the International Space Station, but it does not hold ozone. Pairing ozone with the wrong neighboring layer (mesosphere or troposphere) is the typical slip.

Which type of rock is formed when molten magma cools and solidifies?

Correct answer: Igneous. Igneous rock forms when magma (underground) or lava (surface) cools and crystallizes. Granite is the classic slow-cooled intrusive example; basalt is the fast-cooled extrusive one. Sedimentary rock forms from pressed and cemented sediments like sandstone or limestone and never involves melting. Metamorphic rock starts as another rock that is reshaped by heat and pressure without fully melting, producing slate or marble. Organic is not one of the three official rock-cycle categories, which makes it a distractor designed to look plausible next to the real three.

Which of the following best describes the function of red blood cells?

Correct answer: Transport oxygen throughout the body. Red blood cells carry hemoglobin, an iron-rich protein that grabs oxygen in the lungs and releases it to tissues, then carries some carbon dioxide back. Producing antibodies is the job of white blood cells, specifically B lymphocytes. Clotting is handled by platelets along with clotting factors in plasma. Hormones come from endocrine glands like the thyroid, adrenal, and pituitary, not from blood cells. Confusing red cells with white cells or platelets is the standard trap because all three live in blood and look similar at first glance.

Fight infection by producing antibodies

Newton's Third Law of Motion states that for every action there is:

Correct answer: An equal and opposite reaction. Newton's Third Law says forces come in pairs that are equal in magnitude and opposite in direction, acting on two different bodies. Push on a wall and the wall pushes back on you with the same force. A rocket pushes exhaust gas down and the gas pushes the rocket up by the same amount. The forces act at the same instant, never delayed, which rules out the first choice. They are equal, never greater, which kills the second. Parallel and proportional confuses Third Law with the F=ma scaling of the Second Law.

A greater and opposite reaction

A proportional and parallel reaction

Photosynthesis in plants primarily uses which two resources to produce glucose?

Correct answer: Carbon dioxide and water. Photosynthesis takes carbon dioxide pulled in through leaf stomata and water drawn up from the roots, then uses solar energy captured by chlorophyll to build glucose and release oxygen. Glucose and oxygen are the products, not the inputs, so picking them reverses the equation. Nitrogen and phosphorus matter for plant growth, but they are soil nutrients used in proteins and DNA, not the raw materials for sugar. The simple equation worth memorizing: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂.

Which planet in our solar system is largest by diameter?

Correct answer: Jupiter. Jupiter is the largest planet at roughly 143,000 km in diameter, more than 11 Earths wide and over 300 Earths in mass. Saturn comes in second and is often confused for the biggest because of its prominent rings, which make it look visually huge in photos, but Saturn is actually smaller and far less dense than Jupiter. Uranus and Neptune are the ice giants and are much smaller, each only about four times Earth's diameter. The mental shortcut: Jupiter is the king of the gas giants by size and mass.

In an acid-base reaction, the pH of a neutral solution is:

Correct answer: 7. The pH scale runs from 0 to 14, and 7 sits dead center as the neutral point where hydrogen-ion and hydroxide-ion concentrations are equal. Pure water is the standard example. A pH of 0 marks the strongest common acids like concentrated hydrochloric acid. A pH of 14 marks the strongest bases like concentrated sodium hydroxide. A pH of 10 is mildly basic (think milk of magnesia), not neutral. Each whole-number step represents a tenfold change in hydrogen-ion concentration, so the scale is logarithmic, not linear.

How many free General Science practice questions are here?

This page has 9 free ASVAB General Science questions, each with the correct answer and a full worked explanation. They're free to use with no account required.

Does General Science count toward my AFQT score?

No. General Science is not one of the four AFQT subtests, so it does not affect your AFQT/enlistment score. It does feed line scores that determine which military jobs you qualify for.

What does the General Science subtest cover?

Tests knowledge of physical, biological, and earth sciences. Covers topics you'd see in high school science classes. On the CAT-ASVAB it has 15 questions with about 10 minutes to answer them. Topics include: Biology, chemistry, physics, earth science, ecology.

Are these the same as the real ASVAB questions?

No. These are original practice questions calibrated to match the style and difficulty of the real ASVAB. The actual test is a secure exam, so no one publishes its live items. Practicing this format is the closest legitimate prep.

Free ASVAB General Science Practice Test

9 General Science (GS) practice questions, each with a worked explanation of the right answer.

Last updated May 2026

The ASVAB General Science (GS) subtest covers biology, chemistry, physics, earth science, ecology. On the computer-adaptive CAT-ASVAB it has 15 questions with about 10 minutes to answer. It is not an AFQT subtest, but it feeds the line scores that decide which jobs you qualify for. Work the 9 questions below, then read each explanation. Understanding why the answer is right is what raises your score.

Question 1· General Science
Which organ is primarily responsible for filtering waste products from the blood and producing urine?
- A.Liver
- B.Kidney
- C.Pancreas
- D.Spleen
Show answer & explanationHide answer
Correct answer: B. Kidney
Why: The kidneys filter nitrogen-rich waste and excess water from the blood and excrete them as urine. Each kidney contains roughly a million nephrons that do this filtering work. The liver also processes blood, but its job is detoxifying chemicals, breaking down old red cells, and metabolizing nutrients into bile and proteins, not making urine. The pancreas produces digestive enzymes and the hormone insulin. The spleen filters old red blood cells and stores immune cells but does not produce urine. Urine production is the kidney's defining function.
Question 2· General Science
Water (H₂O) is best classified as which of the following?
- A.An element
- B.A compound
- C.A mixture
- D.An isotope
Show answer & explanationHide answer
Correct answer: B. A compound
Why: A compound is two or more different elements chemically bonded in a fixed ratio, which is exactly what H₂O is: hydrogen and oxygen locked at 2 to 1 by covalent bonds. An element contains only one kind of atom, so water cannot qualify because it holds two. A mixture is a physical blend whose components keep their own identities and can be separated by physical means, like salt water or air, but the H and O in water cannot be separated that way. An isotope describes versions of one element with different neutron counts, not a multi-element substance.
Question 3· General Science
Which layer of Earth's atmosphere contains the ozone layer that absorbs most of the sun's ultraviolet radiation?
- A.Troposphere
- B.Mesosphere
- C.Stratosphere
- D.Thermosphere
Show answer & explanationHide answer
Correct answer: C. Stratosphere
Why: The stratosphere sits roughly 10 to 50 kilometers above the surface, and within it the ozone layer absorbs most incoming UV radiation. The troposphere is the bottom layer where weather happens and airliners cruise; it lacks the ozone concentration. The mesosphere is above the stratosphere and is where meteors burn up. The thermosphere is higher still and hosts auroras and the International Space Station, but it does not hold ozone. Pairing ozone with the wrong neighboring layer (mesosphere or troposphere) is the typical slip.
Question 4· General Science
Which type of rock is formed when molten magma cools and solidifies?
- A.Sedimentary
- B.Metamorphic
- C.Igneous
- D.Organic
Show answer & explanationHide answer
Correct answer: C. Igneous
Why: Igneous rock forms when magma (underground) or lava (surface) cools and crystallizes. Granite is the classic slow-cooled intrusive example; basalt is the fast-cooled extrusive one. Sedimentary rock forms from pressed and cemented sediments like sandstone or limestone and never involves melting. Metamorphic rock starts as another rock that is reshaped by heat and pressure without fully melting, producing slate or marble. Organic is not one of the three official rock-cycle categories, which makes it a distractor designed to look plausible next to the real three.
Question 5· General Science
Which of the following best describes the function of red blood cells?
- A.Fight infection by producing antibodies
- B.Transport oxygen throughout the body
- C.Regulate blood clotting
- D.Produce hormones
Show answer & explanationHide answer
Correct answer: B. Transport oxygen throughout the body
Why: Red blood cells carry hemoglobin, an iron-rich protein that grabs oxygen in the lungs and releases it to tissues, then carries some carbon dioxide back. Producing antibodies is the job of white blood cells, specifically B lymphocytes. Clotting is handled by platelets along with clotting factors in plasma. Hormones come from endocrine glands like the thyroid, adrenal, and pituitary, not from blood cells. Confusing red cells with white cells or platelets is the standard trap because all three live in blood and look similar at first glance.
Question 6· General Science
Newton's Third Law of Motion states that for every action there is:
- A.An equal but delayed reaction
- B.A greater and opposite reaction
- C.An equal and opposite reaction
- D.A proportional and parallel reaction
Show answer & explanationHide answer
Correct answer: C. An equal and opposite reaction
Why: Newton's Third Law says forces come in pairs that are equal in magnitude and opposite in direction, acting on two different bodies. Push on a wall and the wall pushes back on you with the same force. A rocket pushes exhaust gas down and the gas pushes the rocket up by the same amount. The forces act at the same instant, never delayed, which rules out the first choice. They are equal, never greater, which kills the second. Parallel and proportional confuses Third Law with the F=ma scaling of the Second Law.
Question 7· General Science
Photosynthesis in plants primarily uses which two resources to produce glucose?
- A.Oxygen and nitrogen
- B.Carbon dioxide and water
- C.Glucose and oxygen
- D.Nitrogen and phosphorus
Show answer & explanationHide answer
Correct answer: B. Carbon dioxide and water
Why: Photosynthesis takes carbon dioxide pulled in through leaf stomata and water drawn up from the roots, then uses solar energy captured by chlorophyll to build glucose and release oxygen. Glucose and oxygen are the products, not the inputs, so picking them reverses the equation. Nitrogen and phosphorus matter for plant growth, but they are soil nutrients used in proteins and DNA, not the raw materials for sugar. The simple equation worth memorizing: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂.
Question 8· General Science
Which planet in our solar system is largest by diameter?
- A.Saturn
- B.Neptune
- C.Jupiter
- D.Uranus
Show answer & explanationHide answer
Correct answer: C. Jupiter
Why: Jupiter is the largest planet at roughly 143,000 km in diameter, more than 11 Earths wide and over 300 Earths in mass. Saturn comes in second and is often confused for the biggest because of its prominent rings, which make it look visually huge in photos, but Saturn is actually smaller and far less dense than Jupiter. Uranus and Neptune are the ice giants and are much smaller, each only about four times Earth's diameter. The mental shortcut: Jupiter is the king of the gas giants by size and mass.
Question 9· General Science
In an acid-base reaction, the pH of a neutral solution is:
- A.0
- B.7
- C.10
- D.14
Show answer & explanationHide answer
Correct answer: B. 7
Why: The pH scale runs from 0 to 14, and 7 sits dead center as the neutral point where hydrogen-ion and hydroxide-ion concentrations are equal. Pure water is the standard example. A pH of 0 marks the strongest common acids like concentrated hydrochloric acid. A pH of 14 marks the strongest bases like concentrated sodium hydroxide. A pH of 10 is mildly basic (think milk of magnesia), not neutral. Each whole-number step represents a tenfold change in hydrogen-ion concentration, so the scale is logarithmic, not linear.

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What's on the ASVAB General Science subtest

Tests knowledge of physical, biological, and earth sciences. Covers topics you'd see in high school science classes.

Common topics you'll see:

Human body systems
Cell biology & genetics
Chemistry basics (elements, compounds, reactions)
Physics fundamentals (force, energy, waves)
Earth science (weather, geology, astronomy)
Ecology & ecosystems
Scientific method & measurement

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FAQ

How many free General Science practice questions are here?: This page has 9 free ASVAB General Science questions, each with the correct answer and a full worked explanation. They're free to use with no account required.
Does General Science count toward my AFQT score?: No. General Science is not one of the four AFQT subtests, so it does not affect your AFQT/enlistment score. It does feed line scores that determine which military jobs you qualify for.
What does the General Science subtest cover?: Tests knowledge of physical, biological, and earth sciences. Covers topics you'd see in high school science classes. On the CAT-ASVAB it has 15 questions with about 10 minutes to answer them. Topics include: Biology, chemistry, physics, earth science, ecology.
Are these the same as the real ASVAB questions?: No. These are original practice questions calibrated to match the style and difficulty of the real ASVAB. The actual test is a secure exam, so no one publishes its live items. Practicing this format is the closest legitimate prep.

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