049.
M: Are you going to London next weekend?
W: Yes, I will visit a friend of mine while I am there.
答案解析：
正确答案为C。根据I will visit a friend of mine while I am there.我要拜访在那里的朋友。因此C项，拜访朋友正确。

050.
W: Can I help you, sir?
M: Could I change my order? I just want the sandwich and not the soup.
W: I've just handed in your order, sir. I'm not sure if I can change it now. I'll ask the cook.
答案解析：
正确答案为B。根据I've just handed in your order, sir. I'm not sure if I can change it now.我刚把你点的单交上去，我不确定现在是否能改。可知，她刚刚把客人点的单交给厨师，因此B项正确。