问题补充：
I need your help because I don’t know .
A. how to do
B. what to do it
C. what should I do
D. how to do it
答案：
A. how to do
B. what to do it
C. what should I do
(答案→)D. how to do it
解析：本题考查特殊疑问词引导动词不定式的用法。Do是及物动词，需带宾语，而how疑问副词，不可作do的宾语，故A错误；B答案what是疑问代词，可作do的宾语，而it也作do的宾语，故do的宾语多余；答案C是宾语从句，应用陈述句语序才对。
