One evening he heard someone _____his do
题型:选择题
问题:
One evening he heard someone _____ his door. He quickly opened the door and found a stranger. [ ]
A. knocked at
B. knocking at
C. knocking into
One evening he heard someone _____ his door. He quickly opened the door and found a stranger. [ ]
A. knocked at
B. knocking at
C. knocking into