纠结的语法题 帮帮忙

That young man has made so much noise that he______not have allowed to attend the concert.
1.could
2.must
3.would
4.should
答案4
这句的意思是：那个年轻人太吵，本不应该允许他参见音乐会的，有一种后悔让他参加的意味，所以用should.(shouldn't have done something)

-There were already five people in the car but they managed to take me as well.
-It_____a comfortable journry.
1.can't be
2.shouldn't be
3.must have been
4.couldn't have been
答案4 couldn't表过去否定的猜测 放在这怎么好像解释怪怪的？
--这句是说车里已经有了五个人了，但是还是把我也一起载走了，言外之意是车太挤了。听话人所以说，那肯定不是一次舒服的旅行，所以4最合适。

Joel doesn't regret____even if it might have upset Jennifer.
1.to tell her what he thought
2.to tell her that he thought
3.telling her what he thought
4.telling her that he thought
答案3
Joel并不后悔告诉Jennifer她所想的，尽管可能会让Jennifer伤心。
Regret doing something是指后悔做过的事情，这里might have upset是过去时态，所以选4.

前面2道 是1.could
2.must
3.would