问题补充：
- You look worried. Whats the matter?
- I have some problems with my parents. I really don know.
A. who to speak
B. who speaks to
C. who to speak to
D. who speaking to
答案：
A. who to speak
B. who speaks to
(答案→)C. who to speak to
D. who speaking to
解析：句意：你看起来很忧虑，怎么了？我和父母有些问题，我不知道该和谁说。句中所缺的部分是宾语从句，由疑问词who引导，疑问词后用不定式，故选C。
