The world has a big headache and it by money. It began in America last year.A. causeB. ca

问题补充：

The world has a big headache and it by money. It began in America last year.

A. cause

B. causes

C. is caused

D. are caused

答案：

A. cause

B. causes

(答案→)C. is caused

D. are caused

解析：根据句子意思，本题要使用被动语态，所以只能在CD中选择，又因为it 为单数，所以要选择C