69.– Are you sure you have to?It’s been very late.  -- I don’t know ______ I can do it if not now.  A.whereB.whyC.whenD.how

问题描述:

69.– Are you sure you have to?It’s been very late.
  -- I don’t know ______ I can do it if not now.
  A.whereB.whyC.whenD.how

D how后面必须跟it/them作表语 前三个后面不用加

C
如果现在不做,什么时候做

c吧 句子成分完整 主要是根据句意选.if not now 如果不是现在的话 所以前面强调时间 应该是c