At this point he has to stay in the back hallway when we 're not home and at night because he sometimes ca n't wait to be let out before he pees . And he 's gotten really chunky . And I have n't been able to do any agility with him because of the way Prednisone affects muscle tissue .

Generate a question about the above context.
Why is there Prednisone in his muscle tissue ?
Choices: A). He ate something bad; B). He peed in the wrong spot; C). None of the above choices .; D). He is sick;