q: What feeds on plankton and nonliving organic matter?
Options:
- (A) bacteria
- (B) barnacles
- (C) animals
- (D) sharks
- (E) pythons
- (F) graptolites
- (G) molluscs
- (H) bears
a: (G)... Explanation: Bivalves feed on plankton and nonliving organic matter. Bivalve molluscs are very common. Molluscs feed on plankton and nonliving organic matter. That's why the answer is (G).

q: What lacks respiratory and excretory systems?
Options:
- (A) the Sun
- (B) insects
- (C) starfish
- (D) barnacles
- (E) ferns
- (F) water
- (G) Conifers
- (H) humans
a: (C)... Explanation: Echinoderms lack respiratory and excretory systems. Echinoderms are represented by the starfish. Starfish lack respiratory and excretory systems. That's why the answer is (C).

q: Thyroxine increases the rate of metabolism in cells throughout the what?
Options:
- (A) Summer
- (B) body
- (C) state
- (D) skin
- (E) H 2 O
- (F) HIV
- (G) life
- (H) humans
a: (B)... Explanation: Thyroid hormones increase the rate of metabolism in cells throughout the body. Thyroxine, a thyroid hormone, is an aryl iodide. Thyroxine increases the rate of metabolism in cells throughout the body. That's why the answer is (B).

q: What can prevent 90 percent of the body's heat loss?
Options:
- (A) Masks
- (B) fur
- (C) coats
- (D) bald head
- (E) increase body fat
- (F) sweaters
- (G) skin
- (H) hair
a:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
(H)... Explanation: Head hair is especially important in preventing heat loss from the body. Almost 90 percent of the body's heat loss is from the head. Without hair, 90 percent of the body's heat would be lost. That's why the answer is (H).