103.
W: How is your stomach this morning?
M: Much better, thanks.
W: But you should stay in bed for another day or two, and you shouldn't eat too much.
M: But, doctor, I haven't eaten anything for 3 days.
答案解析：
正确答案为B。根据But, doctor, I haven't eaten anything for 3 days. 可是医生，我已经3天没有吃过东西了。可知，二人是医生和患者的关系。因此B项正确。

104.
M: Excuse me. How much is the T-shirt?
W: It's 35 dollars.
M: But it's too small for me. Do you have a bigger one?
W: Yes. Here you are.
答案解析：
正确答案为C。根据How much is the T-shirt? 这件T恤多少钱？和Do you have a bigger one? 你有大号的吗？可知，二人是售货员与顾客的关系。因此C项正确。