________ your letter, I would have started off two days ago.

A．If I received

B．Should I receive

C．If I could have received

D．Had I received

在实际的教学中，有的教师对学生作业采用“漏一补十”“错一罚十”的做法。
问题：你怎样看待这一现象请运用记忆的有关规律加以分析。