34. Differentiation of teeth is greatest in (A) reptiles. (B) mammals. (C) bony fishes. (D) sharks. (E) amphibians.

30. All of the following are reasons why gas exchange is more difficult for aquatic animals than it is for terrestrial animals except (A) water is harder to pump than air. (B) water is denser than air. (C) water contains much less O2 than air per unit volume. (D) gills have less surface area than lungs. (E) exchanging gases with water causes substantial heat loss.