Answer:
D) Trains
Step-by-step explanation:
It takes a very long time for a train to stop.
For example, a freight train carrying around 100 rail cars and travelling at 55 miles per hour needs more than 1 mile to stop if the emergency brake is applied.
A passenger train travelling at 80 miles per hour takes abut 1 mile to stop.
So there is no way a train suddenly stops.