-----I didin't give him a hand when he was in trouble.-----A.should B.ought to haveC.ought to doD.should do为什么选B

-----I didin't give him a hand when he was in trouble.-----A.should B.ought to haveC.ought to doD.should do为什么选B
-----I didin't give him a hand when he was in trouble.
-----A.should B.ought to haveC.ought to doD.should do
为什么选B

-----I didin't give him a hand when he was in trouble.-----A.should B.ought to haveC.ought to doD.should do为什么选B
outht to have done sth.表示“本该做某事（却未做）”,符合题意.

表示过去应该做 但是没有做