Which term denotes the class that includes humans and whales?

• A. Hermatypic
• B. Holothuroidea
• C. Invertebrate
• D. Mammalia

Answer: (D)

Classification by class groups organisms that share key vertebrate traits. Humans and whales are both vertebrates in the phylum Chordata, and they share defining features of mammals: they are warm-blooded, have hair at some stage, and females produce milk to feed their young. These shared characteristics place them in the class Mammalia. The other terms describe different groups: hermatypic refers to reef-building corals, holothuroidea are sea cucumbers (a class of echinoderms), and invertebrate means lacking a backbone, which does not apply to humans or whales. So Mammalia best identifies the group that includes humans and whales.