ASVAB General Science Practice Test

Correct Answer: C. Nucleus

Explanation: The nucleus is the part of the cell that contains the cell's genetic material (DNA).

• Option A (Cytoplasm): Incorrect because the cytoplasm is the jelly-like fluid that fills a cell but does not house the genetic material.
• Option B (Cell membrane): Incorrect as the cell membrane surrounds the cell and controls the movement of substances in and out, but does not contain genetic material.
• Option D (Mitochondria): Incorrect although mitochondria have their own DNA, the primary genetic material of the cell is located in the nucleus.

Correct Answer: C. Cellular respiration

Explanation: Cellular respiration is the process by which cells convert glucose into ATP (adenosine triphosphate), the cell's main energy-carrying molecule, in the presence of oxygen.

• Option A (Fermentation): Incorrect because fermentation is an anaerobic process that occurs without oxygen and produces less ATP than cellular respiration.
• Option B (Photosynthesis): Incorrect as photosynthesis is the process used by plants to convert light energy into chemical energy, not ATP from sugar.
• Option D (Osmosis): Incorrect because osmosis is the movement of water across a semi-permeable membrane and is not involved in energy production.

Correct Answer: B. Gravitational force

Explanation: Gravitational force is the force that keeps the planets in orbit around the sun. It is the attraction between two objects with mass, in this case, the planets and the sun.

• Option A (Electromagnetic force): Incorrect because this force involves electric charges, not the mass of objects like planets and stars.
• Option C (Centrifugal force): Incorrect as centrifugal force is an apparent force observed in a rotating frame of reference and is not what primarily keeps planets in orbit.
• Option D (Nuclear force): Incorrect because nuclear forces operate at the level of subatomic particles and are not responsible for the orbits of planets.

Correct Answer: B. Stratosphere

Explanation: The ozone layer is located in the stratosphere, the second layer of Earth's atmosphere. This layer absorbs and scatters the solar ultraviolet radiation.

• Option A (Troposphere): Incorrect because the troposphere is the lowest layer of Earth's atmosphere and does not contain the ozone layer.
• Option C (Mesosphere): Incorrect as the mesosphere is above the stratosphere and does not contain the ozone layer.
• Option D (Thermosphere): Incorrect because the thermosphere is the uppermost layer of the atmosphere and is too high to contain the ozone layer.

Correct Answer: B. The Sun

Explanation: The Sun is the primary source of energy for Earth's climate system, providing the heat and light necessary for life and weather patterns on Earth.

• Option A (The Moon): Incorrect because the Moon does not provide significant energy to Earth's climate system.
• Option C (Geothermal heat): Incorrect as geothermal heat is a minor source of energy compared to the Sun.
• Option D (Ocean currents): Incorrect because ocean currents distribute heat but are not a primary source of energy.

Correct Answer: A. A substance that increases the reaction rate

Explanation: A catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

• Option B (Consumed in the reaction): Incorrect because a catalyst is not consumed in the reaction; it remains chemically unchanged.
• Option C (Decreases the reaction rate): Incorrect as a catalyst speeds up a reaction, not slows it down.
• Option D (Remains unchanged): This option is partially correct, as a catalyst does remain unchanged, but its primary function is to increase the reaction rate, not just to remain unchanged.

Correct Answer: C. Mass

Explanation: Mass is the term that describes the amount of matter in an object. It is a measure of the object's inertia and is independent of gravity.

• Option A (Weight): Incorrect because weight is the force exerted by gravity on an object and can vary with location.
• Option B (Volume): Incorrect as volume is the amount of space an object occupies, not the amount of matter.
• Option D (Density): Incorrect because density is the mass per unit volume of a substance, not just the amount of matter.

Correct Answer: B. Oxygen

Explanation: Oxygen is the most abundant element in the human body by mass. It is a key component of water and organic molecules, which are essential to human life.

• Option A (Carbon): Incorrect because, although essential for organic molecules, carbon is not as abundant as oxygen by mass.
• Option C (Hydrogen): Incorrect as hydrogen, while abundant by atom count due to its presence in water, is lighter and thus not as abundant by mass.
• Option D (Nitrogen): Incorrect because nitrogen is less abundant in the human body compared to oxygen and carbon.

Correct Answer: C. The position of the Moon relative to the Earth and Sun

Explanation: The phases of the Moon are caused by the changing positions of the Moon, Earth, and Sun. The amount of the Moon that we see lit by the Sun changes as the Moon orbits the Earth.

• Option A (Earth's shadow): Incorrect because the Earth's shadow causes lunar eclipses, not the regular phases of the Moon.
• Option B (Moon's rotation): Incorrect as the Moon's rotation on its axis is synchronized with its orbit around Earth, resulting in the same side always facing Earth.
• Option D (Sun's rotation): Incorrect because the Sun's rotation does not affect the phases of the Moon.

Correct Answer: B. Methane

Explanation: Methane is the primary component of natural gas, making up about 70-90% of natural gas used as fuel.

• Option A (Carbon Dioxide): Incorrect as carbon dioxide is a product of burning natural gas, not a component.
• Option C (Oxygen): Incorrect because oxygen is not a component of natural gas; it is used in the process of combustion of natural gas.
• Option D (Nitrogen): Incorrect as nitrogen is present only in trace amounts in natural gas.

Correct Answer: C. Igneous

Explanation: Igneous rocks are formed from the cooling and solidification of magma or lava.

• Option A (Sedimentary): Incorrect because sedimentary rocks are formed from the compaction and cementation of various sediments.
• Option B (Metamorphic): Incorrect as metamorphic rocks are formed from existing rocks transformed by heat and pressure.
• Option D (Limestone): Incorrect because limestone is a type of sedimentary rock, not igneous.

Correct Answer: D. Producers

Explanation: Producers, such as plants and algae, are organisms that produce their own food through photosynthesis or chemosynthesis.

• Option A (Herbivores): Incorrect as herbivores are consumers that eat plants.
• Option B (Carnivores): Incorrect because carnivores are consumers that eat other animals.
• Option C (Decomposers): Incorrect as decomposers break down dead material and waste products, recycling nutrients back into the ecosystem.

Correct Answer: B. Photosynthesis

Explanation: Chloroplasts in plant cells are primarily responsible for photosynthesis, the process by which plants convert light energy into chemical energy (glucose).

• Option A (Cellular respiration): Incorrect because cellular respiration occurs in the mitochondria, not chloroplasts.
• Option C (Protein synthesis): Incorrect as protein synthesis primarily occurs in the ribosomes.
• Option D (Waste removal): Incorrect because waste removal is not the function of chloroplasts; this process involves various other cell structures.

Correct Answer: C. Both A and B

Explanation: At sea level, water boils at 100°C, which is equivalent to 212°F. These two measurements represent the same temperature in different units.

• Option A (100°C): Correct but incomplete as it only represents the metric unit.
• Option B (212°F): Correct but incomplete as it only represents the imperial unit.
• Option D (0°C): Incorrect because 0°C is the freezing point of water, not the boiling point.

Correct Answer: C. Rusting of iron

Explanation: Rusting of iron is a chemical change because it results in the formation of a new substance (iron oxide), with different properties from iron.

• Option A (Boiling water): Incorrect as boiling water is a physical change; it changes state but not chemical composition.
• Option B (Dissolving sugar in water): Incorrect because this is a physical change; the sugar remains chemically the same.
• Option D (Melting ice): Incorrect as melting ice is a physical change; it changes from solid to liquid without altering its chemical structure.

Correct Answer: C. Brainstem

Explanation: The brainstem plays a crucial role in regulating involuntary functions such as heart rate, breathing, and blood pressure.

• Option A (Cerebrum): Incorrect because the cerebrum is responsible for higher brain functions like thought, memory, and emotion.
• Option B (Cerebellum): Incorrect as the cerebellum is primarily involved in coordination and balance.
• Option D (Hippocampus): Incorrect because the hippocampus is associated with memory and learning, not with regulating heart rate and breathing.

Correct Answer: D. Comet

Explanation: Comets are often described as "dirty snowballs" because they are composed of ice, dust, and frozen gases. As they approach the sun, they heat up and release gas and dust, creating visible tails.

• Option A (Asteroid): Incorrect as asteroids are primarily made of rock and metal.
• Option B (Star): Incorrect as stars are massive luminous celestial bodies made mainly of hydrogen and helium undergoing nuclear fusion.
• Option C (Planet): Incorrect because planets are large celestial bodies orbiting stars, composed of various materials, but not fitting the "dirty snowball" description.

Correct Answer: B. Covalent bond

Explanation: A covalent bond is formed when two atoms share one or more pairs of electrons, typically between non-metal atoms.

• Option A (Ionic bond): Incorrect because an ionic bond is formed when one atom donates electrons to another atom, typically between a metal and a non-metal.
• Option C (Metallic bond): Incorrect as metallic bonds occur between metal atoms, where electrons are shared in a lattice.
• Option D (Hydrogen bond): Incorrect because a hydrogen bond is a weak bond between two molecules resulting from an electrostatic attraction between a proton in one molecule and an electronegative atom in the other.

Correct Answer: C. Nitrogen

Explanation: Nitrogen makes up about 78% of Earth's atmosphere, which is more than any other gas.

• Option A (Oxygen): Incorrect because although essential for life, oxygen makes up only about 21% of the Earth's atmosphere.
• Option B (Carbon Dioxide): Incorrect because carbon dioxide is a minor component of the atmosphere, constituting only about 0.04%.
• Option D (Hydrogen): Incorrect as hydrogen is a very light gas and is present only in trace amounts in the atmosphere.

Correct Answer: B. To carry oxygen

Explanation: Red blood cells are primarily responsible for carrying oxygen from the lungs to the body's tissues and returning carbon dioxide from the tissues back to the lungs. This is facilitated by the protein hemoglobin, which is present in red blood cells.

Option A (To fight infection): Incorrect because fighting infection is primarily the function of white blood cells, not red blood cells. White blood cells are part of the immune system and help the body to fight off infections and other diseases.

Option C (To clot blood): Incorrect because clotting of blood is mainly facilitated by platelets and clotting factors, not red blood cells. Platelets are small cell fragments that help in forming blood clots and stop bleeding.

Option D (To remove waste): Incorrect because the removal of waste from the body is a function largely carried out by the kidneys and liver, not red blood cells. The kidneys filter waste products from the blood to form urine, and the liver breaks down waste products in the blood, which are then eliminated from the body.