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.
