Cylinder and a sphere

I think the answer is (A).

The volume of a cylinder is expressed as Pi*(r^2)*h, such that r=radius of circular cylindrical base and h=height of cylinder.
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The volume of a sphere is expressed as (4/3)*Pi*(r^3), such that r=radius of sphere.

For both the height AND radius of the cylinder to equal the radius of the sphere, the height and radius of the cylinder must be equal to each other, or h=r.

Therefore, the volume of this particular cylinder = Pi*(r^2)*r = Pi*(r^3)

Since the volume of the sphere is (4/3)*Pi*(r^3), the volume of the sphere = (4/3)*(volume of cylinder)

Therefore, the sphere holds a volume of (4/3)*(30 liters of water) = 40 liters of water.
After moving all 30 liters of water from the cylinder to the sphere, the sphere can still hold another 10 liters of water, or 1/4 of its total capacity.