Question

【题目】Listen! Someone at the door. Please go and answer it.
A.knocks
B.is knocking
C.has knocked
D.was knocking

Answer 1

【答案】B
【解析】句意：听!有人在敲门。请去看一看。像Listen，look， now等表示现在时间，要用现在进行时态，现在进行时的构成：be+doing；根据Listen!可知现在的时间，要用现在进行时态，结合句意和语境可知选B。