—"I'm sorry I forgot _____ the letter for you!"

—"It doesn't matter, I'll post it myself." [ ]

A. to post

B. posting

C. post

D. posted

The reason _______ he gave at the meeting was not the exact reason _______ he failed to show up on time.

A．why; that

B．which; that

C．that; why

D．that; which