Read the following context and choose the best option to answer the question.
Context: Seph ate way more than I did , I doubted he could always eat like that and yet keep so skinny ... Both of us crept up the stairs and said goodnight to eachother . I settled down into my bed and tried to sleep . Rain lashed at the windows , and thunder shook the entire house .
Question: What may be the reason why they do n't think Seph will stay skinny ?
Options: 
A. None of the above choices .
B. He is n't eating very healthy .
C. He is already getting a gut .
D. Metabolism slows down as you age .


D