Consider a box sitting in the back of a pickup truck that accelerates toward the right. Because the bed of the pickup is rough, the box does not slide. What is the reason for the box not sliding?
1) The friction between the box and the bed of the pickup prevents sliding.
2) The acceleration of the truck causes the box to stay in place.
3) The weight of the box keeps it from sliding.
4) The rough surface of the pickup bed provides enough grip for the box to stay in place.