What are the characteristics of vertebrates?
a. They have an internal skeleton composed of articulated vertebrae.
b. They have a body divided into three well-differentiated zones: the head, the trunk, and the extremities.
c. They have a well-developed nervous system, protected by the skeleton.
d. They have two types of respiratory systems: gills for aquatic animals and lungs for terrestrial animals.
e. They have a digestive system that varies according to their diet.
f. They have a circulatory system composed of blood vessels and a pump, the heart.
g. They reproduce sexually, with external fertilization in aquatic animals and internal fertilization in terrestrial animals.
h. They have a pointed or fusiform body, with scales and fins for swimming.

a) a, b, c, d, e, f, g, h
b) b, c, d, e, f, g, h
c) a, b, c, d, e, f, h
d) b, d, e, f, g, h