What mammals have a high energy requirement and generate heat?
cats bats Crustaceans bears frogs lizards birds mammals
A B C D E F G H
Birds have a high metabolic rate and a high energy requirement.
birds are mammals that generate heat and have a high energy requirement 
What mammals have a high energy requirement and generate heat? (A) cats (B) bats (C) Crustaceans (D) bears (E) frogs (F) lizards (G) birds (H) mammals