As a matter of fact this sofa is now an antique which served a bed in the past .A. asB.

问题补充：

As a matter of fact , this sofa is now an antique which served a bed in the past .

A. as

B. for

C. to

D. with

答案：

(答案→)A. as

B. for

C. to

D. with

解析：考查词组;serve as担当，充当，句意是;事实上，这个过去充当床的沙发现在是古董。选A。