The couple ______at this time yesterday. Nobody knew when they stopped.
#50618
A
heard quarrelling
B
heard to quarrel
C
were heard quarrelling
D
was heard to quarrel
推荐题目
The children were made ____ 12 hours a day.
#50586
A
work
B
worked
C
working
D
to work
Students should do everything they can __their study. 
#50600
A
improve
B
to improve
C
improving
D
improved