为你解答.
It's time to decide what to do and （A.when to do it）.
是时候决定要做什么和什么时候做了.
解释：括号中可填宾语从句,或是疑问词加不定式.错误选项分析----
B、when to do：缺少了宾语it.
C、when I should do：也缺少宾语.
D、how should I do it：语序错误,应该是陈述语序,改为 I should 才对.