Given the question: Answer the following question given this paragraph: Like amphibians, reptiles are ectotherms with a slow metabolic rate. Their metabolism doesn't generate enough energy to keep their body temperature stable. Instead, reptiles regulate their body temperature through their behavior. For example, the crocodile in Figure below is soaking up heat from the environment by basking in the sun. Because of their ectothermy, reptiles can get by with as little as one tenth the food needed by endotherms such as mammals. Some species of reptiles can go several weeks between meals. Q: A reptile's what doesn't generate enough energy to keep their body temperature stable? Choices: - respiration - tissue - skin - metabolism A:
The answer is:
metabolism