问题补充：
---I am going to Nanjing and stay there for a week.
---you are there, would you please buy some books for me?
A. If
B. While
C. Since
D. As soon as
答案：
A. If
(答案→)B. While
C. Since
D. As soon as
解析：句意：我将要去南京并在那里呆一周。当你在那里时，你能为我买一些书吗？A如果B当……，表示一件事情在发生的过程中另一件事情发生了。强调一段时间，C自从……，D一……就……，故选B.
