The phone had been ringing for three minutes before it            .
#104247
A
answered
B
had answered
C
was answering
D
was answered
推荐题目
By the time Billy was 6, he         in the sea.
#101498
A
had already swum
B
was already swimming
C
has already swum
D
already swam
Three fourths of the homework _______ today.
#103523
A
has finished
B
has been finished
C
have finished
D
have been finished