Velocity is how fast it moves and in what direction it moves in.
Acceleration is the change in how fast it moves. I.e. if it speed up or slows down.
Here we are not given a speed, but we are told that Usain Bolt can increase it (change it) faster than any other runner which means we have been given a change in speed (acceleration, speeding up), therefore it is acceleration.
C. We take subject tests to demonstrate our strengths to increase the chances of admission into a particular school in a university, such as the school of engineering.
