q: What do trees release during the day but not at night?
Options:
- (A) Energy
- (B) water
- (C) He
- (D) Ce
- (E) chemicals
- (F) Energy.
- (G) heat
- (H) oxygen
a: (H)... Explanation: Plants release oxygen during the day but not during the night. All plants are trees. Trees release oxygen during the day but not at night. That's why the answer is (H).

q: What is one thing studied in immunology?
Options:
- (A) illness
- (B) antigens
- (C) humanism
- (D) health
- (E) philosophy
- (F) resistance
- (G) symbology
- (H) fever
a: (B)... Explanation: Antigens are molecules that the immune system recognizes as foreign to the body. Immunology is the study of the immune system. Immunology includes the study of antigens. That's why the answer is (B).

q: What does the substance that male dogs have in urine to mark their territory do?
Options:
- (A) sweating
- (B) attract females
- (C) Release energy
- (D) repels females
- (E) attract enemies
- (F) attract males
- (G) adding heat
- (H) dangerous
a: (B)... Explanation: Male dogs use pheromones in urine to mark their territory. Males produce 'pheromones' to attract females. Male dogs use something that attracts females in urine to mark their territory. That's why the answer is (B).

q: How do salamanders usually find sexual partners?
Options:
- (A) mouth of rivers
- (B) It helps them survive
- (C) interact
- (D) it needs them
- (E) competition
- (F) movement
- (G) sense of smell
- (H) heat produced
a:
(G)... Explanation: Most salamanders use their sense of smell to find a mate. To couple in sexual union, to be matched or mated. Most salamanders find sexual partners by their sense of smell. That's why the answer is (G).