, 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
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(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。