问题补充：
The couple at this time yesterday. Nobody knew when they stopped.
A. heard quarrelling
B. heard to quarrel
C. were heard quarrelling
D. was heard to quarrel
答案：
A. heard quarrelling
B. heard to quarrel
(答案→)C. were heard quarrelling
D. was heard to quarrel
解析：考查时态及语态.句意:昨天这个时候听到这对夫妇吵架了.没有人直到他们什么时候停止的.结合语境可知前文描述的是过去某时的动作,句子主语是动作对象,故用被动语态.现在分词作状语表示正在进行的伴随性动作,这对夫妇是复数形式,故助动词用复数,结合语境可知选C.
