Anna is often heard songs in her room.A. sungB. singingC. singD. to sing

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A. sung
B. singing
C. sing
(答案→)D. to sing
解析：考查非谓语动词。句中考查hear sb do sth听到某人做某事，结构为省to的不定式，其被动应当加上to。句意：常听到安娜在她房间里唱歌。