They were (used to) (hear) him (singing) in a cheerful voice in the classroom when he thou
职称英语
已帮助 人
They were (used to) (hear) him (singing) in a cheerful voice in the classroom when he thought (no one) was near.
A.used to
B.hear
C.singing
D.no one
请帮忙给出正确答案和分析,谢谢!
