Apool player hit a ball with a mass of 0.25kg. the ball travels at a velocity of 15 m/s for 0.75 s until it hits the side of the pool table.

what additional information is required to determine the ball's weight?

a.
the force of inertia acting on the pool cue

b.
the displacement of the pool ball

c.
the value in m/s² of gravity acting on the pool ball

d.
the distance to the nearest pocket in the table

Assuming that the pool hall is located somewhere on Earth,
you don't need any additional information.  In fact, you already
have more than you need.

              Weight = (mass) times (acceleration of gravity) .

The question tells you the mass of the ball, and everybody
knows that the acceleration of gravity on Earth is  9.8 m/s² .
So the weight of the ball is

       (0.25 kg) x (9.8 m/s²)  =  2.45 newtons.

I suppose if you momentarily forgot the acceleration of gravity,
then you'd need somebody to remind you, and that would be
choice 'C', but it would not have to be in m/s².  It could be in
any convenient units of acceleration, and you could easily
convert it to  m/s²  before doing the calculation.