A right circular cylinder and a sphere are of equal volumes and their radii are also equal. If h is the height of the cylinder and d, the diameter of the sphere, then :

• A. $h = d$$
• B. $2h = d$$
• C. $\frac{h}{3} = \frac{d}{2}$$
• D. $\frac{h}{2} = \frac{d}{3}$$