问题补充：
---I’m going to Hangzhou for a holiday this weekend.
--- you are there, could you buy me some green tea?
A. Because
B. While
C. During
D. As
答案：
A. Because
(答案→)B. While
C. During
D. As
解析：句意：我打算这个周末去杭州度假。你在那儿时，给我买些绿茶，好吗？because因为；while当…的时候；during在…期间；as当…时，由于。所以选A。
