Ateam of engineers has designed a new anti-collision device for cars. the device is intended to reduce the chance of collisions between cars. the engineers have decided to test the device on model cars in laboratory conditions before testing it on real cars.

which test would be most useful to decide if the device works as intended?
a) comparing the frequency of collisions with and without the device
b) measuring the amount of damage after a collision, with the device fitted
c) observing how the number of collisions varies with the speed of the cars
d) comparing the performance of the device with that of other similar devices