3) C

Formula for kinetic energy = ½mv²
Let mass of P and Q be ‘m’
KE of P = ½m10² = 50m J
KE of Q = ½m20² = 200m J

So, KE of Q is four times P
The squared in the KE formula makes it four times.

Then the height of Q will be twice of P.
So GPE of Q would be twice as much as P.
This corresponds to option C.