Mary ______ my letter; otherwise she would have replied before now.A.has receivedB.ought to have receivedC.couldn’t have receivedD.shouldn’t have received为什么不是D

Question

Mary ______ my letter; otherwise she would have replied before now.
A.has received
B.ought to have received
C.couldn’t have received
D.shouldn’t have received
为什么不是D

Answer 1

这题选C
couldn't have done 意为“很可能还没做”,客观性强,相对于must have done （很可能做了）来说.
句子意思：玛丽可能还没有收到了我的信；否则她在此之前就回复了.【“她没有回复”是一个客观依据,虽然不能充分证明“她没有收到我的信”】
shouldn't have done 意为“应该还没做“,表达主观性强
She shouldn't have left work yet.I'll call her office.（她应该还没下班.我打她办公室电话看看.）