no one is sure who discovered America .A. As a matter of factB. As the fact of matterC.

问题补充：

, no one is sure who discovered America .

A. As a matter of fact

B. As the fact of matter

C. As the matter of fact

D. As a factual matter

答案：

(答案→)A. As a matter of fact

B. As the fact of matter

C. As the matter of fact

D. As a factual matter

解析：As a matter of fact为固定搭配意为“实际上”。句意：实际上没人确定谁发现了美洲。