Question: Fact 1: Mammals generate heat mainly by keeping their metabolic rate high.  Fact 2: Birds have a high metabolic rate and a high energy requirement.  Given the two facts above, answer the question "What mammals have a high energy requirement and generate heat?" with the following options:  - cats  - bats  - Crustaceans  - bears  - frogs  - lizards  - birds  - mammals
Answer:
birds