一些英语问题,麻烦说下理由哦It can't be our English teacher.It ____ be our

一些英语问题,麻烦说下理由哦
It can't be our English teacher.It ____ be our Chinese teacher because our Chinese teacher is much taller than English teacher
用can还是must,还有这句主语为什么是it
—Emma has been ill for a week.Is she all right now?
—_____.The teacher says she can come to school tomorrow.
A.I hope so B.That's it C.I'm afraid not D.that's ok
Was it under the tree ____ you were away talking to a friend?
Sure.But when I get back there,the bike was gone.
A.that B.where C.which D.while
Do you agree that a_______ help to sell goods?
还有看首字母写词语我总是不知道该写什么怎么办啊?