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

问题补充：

Anna is often heard songs in her room.

A. sung

B. singing

C. sing

D. to sing

答案：

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。