The US/UK war against Iraq and the suffering caused have become a big concern all over th

问题补充：

The US/UK war against Iraq and the suffering caused have become a big concern all over the world.

A. what

B. which

C. it

D. ×

答案：

@@A. what@@B. which@@(答案)C. it@@D. ×

解析：it (= the US/UK war) caused是定语从句修饰the suffering。