问题补充：
He isn’t very successful a singer but he is quite known his music.
A. for;as
B. as;to
C. as;for
D. for;to
答案：
A. for;as
B. as;to
(答案→)C. as;for
D. for;to
解析：此题目的在于考查介词在具体语境中的具体含义。要对此题作出正确的选择,最重要的是要了解介词as和for在此句中的正确含义。as在此句中表示“作为”；for因为,be known for意为“因……而出名”。而be known to意为“为某人所知”,故C项正确。
