Safety belts protect people in cars in the event of an accident because, according to Newton’s laws of motion, when an impact causes the car to suddenly change its motion - A. the speed of the people always increases, since now they have not one but two forces acting on them.
B. the speed of the car always increases, giving it greater force since the mass will remain the same.
C. the car now has a greater overall mass - its own mass plus the mass of the object by which it has been struck.
D. the people in the car will continue to move in the same direction and at the same speed as before the impact.