问题
_____, the car stopped all at once. [ ]
A: Seeing a boy lying on the ground
B: On seeing a boy sitting on the road
C: The driver saw a boy standing on the road
D: The minute the driver saw a boy seated on the road
B: On seeing a boy sitting on the road
C: The driver saw a boy standing on the road
D: The minute the driver saw a boy seated on the road
正确答案是：
