In Most Species, the Female Frog Lays Her Eggs Directly

Multiple Choice

In most species, the female frog lays her eggs directly in the water as a male clasps her back and releases sperm. The fertilized eggs hatch into legless, aquatic tadpoles. Most tadpoles feed on algae, and have gills. As they mature, tadpoles develop legs and lungs, lose the tail, and acquire carnivorous tastes.
-The primary function of external gills in aquatic animals is to

A) transport blood.
B) secrete reproductive hormones.
C) relay nerve impulses.
D) exchange gases with the water.
E) defend against invading microorganisms.