1.A war is so cruel that it always cause great losses,—has h

1.A war is so cruel that it always cause great losses,—has happened in Iraq and another countries.
A what B which C as D one
2._is mentioned above,the number of the students in senior high schools is increasing.
A Which B As C The D It
1选C 2选B 我想知道这是怎么解.
恩,还有代词中as 和which都可代指整件事,那么要怎么区别二者的用法.
我怎么听老师说as 和which都可代指一整件事情呢。
不不不，我想知道的只是当它们二者都作为连词，并且都代替整件事情的时候的区别，