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