HESI A2 Practice Test

Answer: A - Whale. Mammals are characterized by having mammary glands and giving birth to live young. Of the animals on this list, only whales fit that description.

Key Takeaway: Mammals are also characterized as being vertebrates. The chicken is a type of fowl, that like other fowl gives birth to hard eggs. The snake is a reptile, which gives birth to soft eggs. The grasshopper is an invertebrate insect with a hard exoskeleton. The protozoon is a unicellular organism without specialized cellular components.