The volume of a spherical hot air balloon is 36 cubic meters. The burner was turned on to heat the gas trapped in the balloon. The heated gas in the balloon expanded so that the radius of the hot air balloon is now twice the original radius. What is the ratio of the new volume of the hot air balloon to its original volume? A. 2:1 B. 4:3 C. 3:4 D. 8:1