Physics: Systems ?
A. The force diagram for the top box would include a force of gravity and the system's force diagram would not.
B. The force diagram for the top box would include a frictional force acting on it while the system's force diagram would not.
C. The force diagram of the top box would not include friction but the system's force diagram would.
D. The force diagram for the top box would include a normal force while the force diagram for the system would not.