Which of the following can be inferred about warm-blooded animals solely on the basis of information in the passage? A. The body temperatures of warm-blooded animals cannot be easily controlled in the laboratory. B. Warm-blooded animals require more iron in periods of stress than they do at other times. C. Warm-blooded animals are more comfortable at an environmental temperature of 37℃ than they are at a temperature of 42℃. D. In warm-blooded animals, bacteria are responsible for the production of siderophores, which, in turn, make iron available to the animal. E. In warm-blooded animals, infections that lead to fever are usually traceable to bacteria.