50分悬赏：必须专业.20.---- I suppose you were very busy yesterday be

50分悬赏：必须专业.
20.---- I suppose you were very busy yesterday because it was your turn to clean the classroom.
---- _________I asked for leave yesterday.
A.You are welcome.
B.No,I don't think so.
C.Not at all.
D.Maybe you are right.
老师说这道题的答案是B,可是我怎么总觉得怪怪的.真的是选B吗.说说理由.
（ ）____the man there be our new teacher?
He___be,but I am not sure,
A,May;mustn't B.Can;may C.Miust;can't D.Can;can't
老师说这道题答案选D,我觉得更奇怪了.我一开始选的是B,因为有一句“but I am not sure”嘛,但是老师说什么不要按中文的思维想.真的是选D吗.
第一题我明白了,请问第二题到底是选B还是选D.