You shouldnt have asked the boy to run across the street to buy cigarettes; he______by a p

You shouldnt have asked the boy to run across the street to buy cigarettes; he______by a passing car.

A．may be knocked down

B．should have been knocked off

C．might have been knocked down

D．will have been knocked down

请帮忙给出正确答案和分析，谢谢！