The correct option is C The sound could not be heard anymore.
Sound waves need medium to propagate from one point to another such as a solid, liquid, or gas. The sound waves move through each of these mediums by vibrating the molecules in the matter. The molecules in solids are packed very tightly. Liquids are not packed as tightly as solids. And gases are very loosely packed. The spacing of the molecules enables sound to travel much faster through a solid than a gas. Sound travels about four times faster and farther in water than it does in air.
When air is pumped out from the jar by this process, vacuum will creat inside the jar which not allow to propagate sound wave.
Hence, when the bell rings, sound cannot be heard by anyone. (Option C)