B IS YOUR ANSWER.
Soft sound has small amplitude and louder sound has large amplitude. Since, the second wave has large amplitude, it will have the loudest sound.
"Constant velocity" is practically a definition for zero acceleration.
A machine can never be 100% efficient because some work is always lost
due to the lack of materials or equipment that would convert work by 100%. It follows
the second law of entropy. The ideal engine is known as Carnot’s engine having
a 100% efficiency. So far, no engine has ever gotten to 100%.
Distance traveled by the ball is given by

here we know that
speed = 20 m/s
times = 0.25 s
now we have


so ball will travel 5 m distance in the given interval of time