1. What is the main target organ for insulin, the hormone produced by the pancreas?

A. Liver
B. Kidneys
C. Muscles
D. Brain

Correct answer: C

Rationale: The correct answer is C: Muscles. Insulin is a hormone produced by the pancreas that plays a crucial role in regulating blood sugar levels. Its main target organs are the liver, muscles, and adipose tissue. Insulin acts on muscle cells to promote glucose uptake and storage as glycogen, helping to lower blood sugar levels. While the liver and adipose tissue are also important targets for insulin, muscles are particularly significant for glucose utilization and storage. Therefore, muscles are considered the main target organ for insulin in the body.

2. The term "bioaccumulate" refers to...

A. The natural decomposition of organic materials.
B. The buildup of a substance in living organisms.
C. The contamination of seawater with chemical pollutants.
D. The physical entanglement of animals with plastic debris.

Correct answer: B

Rationale: The passage describes microplastics entering food chains and accumulating in organisms, aligning with bioaccumulation.

3. What mineral is essential for muscle function and can cause cramps if deficient?

A. Sodium
B. Calcium
C. Potassium
D. Magnesium

Correct answer: B

Rationale: The correct answer is B: Calcium. Calcium is essential for muscle function, including muscle contraction and relaxation. A deficiency in calcium can lead to muscle cramps and spasms. While sodium, potassium, and magnesium are also important for muscle function, calcium specifically plays a crucial role in muscle contractions. Therefore, calcium is the mineral that is essential for muscle function and can cause cramps if deficient.

4. The human eye focuses light by adjusting the shape of its:

A. Cornea
B. Iris
C. Lens
D. Retina

Correct answer: C

Rationale: The human eye focuses light by adjusting the shape of its lens. The cornea is the transparent outer covering of the eye that helps to focus light, but it does not change shape. The iris regulates the amount of light entering the eye through the pupil but does not adjust the shape of the light. The retina is the layer at the back of the eye that receives and processes light signals but does not play a role in focusing light. Therefore, the correct answer is C, the lens, as it changes shape to focus light onto the retina, allowing for clear vision.

5. Which of the following is an example of an aromatic hydrocarbon?

A. Ethane
B. Benzene
C. Propane
D. Butene

Correct answer: B

Rationale: Benzene is an example of an aromatic hydrocarbon. The other choices are aliphatic hydrocarbons.

6. What happens to the density of a substance if its mass increases while its volume remains constant?

A. Density increases
B. Density decreases
C. Density remains constant
D. Density becomes zero

Correct answer: a

Rationale: Density is the ratio of mass to volume. If the mass increases while the volume remains constant, the density will increase as there is more mass in the same volume.