[Q] What does head hair prevent the loss of?
Options:
- (A) matter
- (B) chemicals
- (C) energy
- (D) sunlight
- (E) Nutrients
- (F) warmth
- (G) humidity
- (H) sweating
[A] Here's my solution: Head hair is especially important in preventing heat loss from the body. Basically, heat is energy. Head hair is especially important in preventing energy loss from the body. The answer is (C).

[Q] A duckbill platypus is a mammal that reproduces how?
Options:
- (A) asexually
- (B) during the day
- (C) by cloning
- (D) spread flower seeds
- (E) They have thick fur
- (F) by laying eggs
- (G) with their fur
- (H) swans
[A] Here's my solution: Monotremes are mammals that reproduce by laying eggs. Monotremes include the duckbill platypus. Duckbill platypus are mammals that reproduce by laying eggs. The answer is (F).

[Q] For animals, displays of color can be viewed as:
Options:
- (A) spectrum
- (B) prudishness
- (C) rainbow
- (D) courtship
- (E) positive
- (F) harm them
- (G) produce light
- (H) Movement
[A] Here's my solution: Courtship is behavior that is intended to attract a mate. Almost all animals display colors to attract a mate or to scare off a predator. Courtship can be manifested by displays of color. The answer is (D).

[Q] Harm to the respiratory and circulatory systems can come from
Options:
- (A) Greenhouse gases
- (B) hydrocarbons
- (C) Sulfur dioxide
- (D) nitrogen oxides
- (E) burning coal
- (F) fossil fuels
- (G) emissions
- (H) Greenhouse gasses
[A]
Here's my solution: Air pollution harms the respiratory and circulatory systems. Nitrogen oxides cause air pollution. Nitrogen oxides harms the respiratory and circulatory systems. The answer is (D).