Statement(A) : 'Elasticity' property is necessary for the propagation of sound.
Statement(B) : In a stationary wave, the rate of transfer of energy across any section is zero.

Since sound waves are carried from one location to another by the molecules of solids, liquids, and gases, sound requires a physical medium for propagation, such as a solid, liquid, or gas. As there are no molecules in the vacuum that can vibrate and convey sound waves, sound cannot travel through it.

When reflected waves from one end of the medium interfere with incident waves from the source due to the source's vibrational frequency, a standing wave pattern is formed within the medium. Because of this interference, certain locations along the medium seem to be at a standstill. The pattern is frequently referred to as a standing wave pattern because the observed wave pattern is marked by points that appear to be standing still. There is no energy transmission since the vibrations of every point remain in place.