Final answer:
A lemur is a prosimian, distinguished from anthropoid primates like humans, chimpanzees, and gorillas by its smaller size and nocturnal habits.
Step-by-step explanation:
The correct answer to which of the following is a prosimian is a. lemur. Prosimians are a group of primates that include species such as the lemurs of Madagascar, tarsiers of Southeast Asia, and the bush babies of Africa. Unlike chimpanzees (c), humans (b), and gorillas (d), which are categorized as anthropoids, lemurs are considered more primitive and display different characteristics such as being smaller and often nocturnal.