Mum my trousers are old. I want to buy a new .A. one B. trousersC. pairD. it

问题补充：

Mum, my trousers are old. I want to buy a new .

A. one

B. trousers

C. pair

D. it

答案：

A. one

B. trousers

(答案→)C. pair

D. it

解析：表示一条裤子要用a pair of trousers,所以说想买条新的要用a new pair