Though I have often heard this song . I have never heard you it.A. being sung sangB. san

问题补充：

Though I have often heard this song . I have never heard you it.

A. being sung, sang

B. sang, singing

C. sung, sing

D. to be sung, to sing

答案：

A. being sung, sang

B. sang, singing

(答案→)C. sung, sing

D. to be sung, to sing

解析：第一空填 sung，因为 song 与 sing 是被动关系；第二空填 sing，因为 you 与 sing 是主动关系。