We are planning to have a surprise party her fifteenth birthday.A. atB. inC. forD. with

问题补充：

We are planning to have a surprise party her fifteenth birthday.

A. at

B. in

C. for

D. with

答案：

A. at

B. in

(答案→)C. for

D. with

解析：at 在时间空间的一点； in在一个空间时间范围内；for为了，对于；with 伴随，用。句意：为了他的第十五个生日，我们正计划举行一个惊喜的聚会。结合语境可知选C。