4._____ the few who have failed their examinations,all the s

4._____ the few who have failed their examinations,all the students in the hall are in very high spirits.
a.Except for b.Besides c.Due to d.Apart from
5.It _______ a fine day,we went for a walk.
a.is b.be c.being d.to be
6.You ________ a letter to him.However,you didn’t .
a.ought to write b.ought to have written
c.should write d.should be writing
7.You _______ be tired; you have only just begun to work.
a.can not b.should not c.mustn’t d.may not
8.All _______ is a nice meal.
a.what I want b.that I want c.the thing I wanted d.which I want
请选择并讲讲为什么.