Answer:
As the device is intended to reduce the chance of collision between cars, the test used has to address this issue hence the answer is A. B tests the amount of damage which is not what the device is intended to do. C addresses the device functionality with respect to the speed of the car which is irrelevant as the device should reduce chance of collision irregardless of the car's speed. D would be useful to test the device although it will not be the most useful to test if the device works as intended, this would probably be used in a later stage of testing to determine the performance and consistency of the device, for example.
