A、The pear. B、The weather. C、The seafood. D、The cold. C细节推断题。对话中agree with sb. 的意思是“对某人的胃口”。由男士话中的seafood很容易得知男士吃了海鲜胃不舒服。故正确答案为C

M：I forgot to bring my pencil and paper to take notes with in class. I left them on my table when I got out this morning.
W：That’s all right. I have enough for both of us.
Q：What will the woman most probably do?

W：You don’t feel very well, do you? You look pale, have you got a cold?
M：Oh, no, but my stomach aches. Maybe the seafood doesn’t agree with me. I have to see my doctor at once.
Q：What probably caused the man’s stomachache?