Option B) 20 m^3 is the correct answer.
Volume of cylinder = pi r^2 h = 30 m^3
Volume of sphere = 4/3 pi r^3
now h = 2r ( given)
so volume of cylinder = pi r^2 * 2r = 2 pi r^3 = 30
pi r^3 = 15 so r^3 = 15/pi
therefore the volume of sphere = 4/3 pi * 15/pi = 4/3 * 15 = 20 m^3