有几道英语题目麻烦大家帮帮忙，并说明原因，谢谢

Question

1.Mary my letter; otherwise she would have replied before now.
A.couldn't have received B.ought to have received D.shouldn't have received. 答案是A
2.My pain apparent the moment i walked into the room,for the first man i met asked sympathetically:"are you feeling all right?" a.Must be B.had been C.must have been D.had to be 答案是C

Answer 1

1、couldn't have done指不可能做了某事，ought to have done指应该做了某事，shouldn't have done指本不该做却做了某事，根据原文的后半句“否则她会在现在之前就回复了”，A为正确答案。
2、根据后半句时态可知，“我的疼痛很明显”发生在过去，对the first man说的are you feeling all right表推测，所以答案为C，大意是“我的疼痛在我进门时一定很明显，因为我见到的第一个人同情地问我‘还好吗？’”。

Answer 2

第一题中couldn't have done表示对过去的否定的推测，表示一种可能性；ought to have done 表示本应该做的事没有做，shouldn't have done 表示过去不应该做某事
第二题中是对过去的肯定推测，只能用must have done sth

Answer 3

1.玛丽应该没收到我的信，否则她早就回复了。B意思为应该收到了，跟题意相反，D意思为不应该收到，表达不正确。故选A
2.我在进屋时一定明显感到了疼痛，因为我遇到的第一个人同情地问我是否无恙？感到疼痛发生在第一个人问我之前，第一个人问我是过去时，过去的过去要用过去完成时，而且题中表示很确定的推测，所以选C。