Answer
a. C, B, A
b. A=B=C
Work Step by Step
The acceleration of each ball is $10 \frac{m}{s^{2}}$ at all times, directed downward. Freefall acceleration is discussed on pages 46-49.
One second after being thrown, ball A is at rest.
One second after being thrown, ball B is moving at 5 m/s upward.
One second after being thrown, ball C is moving at -7 m/s, which is a speed of 7 m/s directed downward.
Ball C is moving faster than any other ball, because speed is the magnitude of the velocity, irrespective of direction.
