Please choose the correct answer to the question: John's pet frog was sick because it wasn't staying warm enough. Maybe

Answer1: The frog was getting burned by a heat lamp Answer2: the frog was unable to regulate its body temperature without an external heat source Answer3: The frog was using too much ice in its drinks Answer4: The water in the tank had dried up.

Answer format: answer1/answer2/answer3/answer4
Answer: answer2