问题:
While dancing happily at home,________.
[ ]
A.the door bell rang
B.the door bell rings
C.we heard the door bell rings
D.we heard the door bell ring
While dancing happily at home,________.
B.the door bell rings
C.we heard the door bell rings
D.we heard the door bell ring
[ ]
A.the door bell rang B.the door bell rings
C.we heard the door bell rings
D.we heard the door bell ring
参考答案: