A red ball was rolling at a speed of 5 m/s. It hit a blue ball that was sitting still. The balls are the same except for their color. What happened to the blue ball once it was hit?
A. It rolled away at more than 5 m/s.
B. It stayed sitting still.
C. It rolled away at 5 m/s.
D. It rolled away at less than 5 m/s.