When a longitudinal wave moves through a certain medium, the quantity which is transmitted through the medium is

The correct answer is (b).

A longitudinal wave is a wave in which the particles of the medium move in the same direction as the wave travels. The energy of a longitudinal wave is carried by the particles of the medium as they move back and forth. The material of the medium is not transmitted through the medium, only the energy.

Option (a) is incorrect because the material of the medium is not transmitted through the medium. The particles of the medium move back and forth, but the material itself does not move.

Option (c) is incorrect because only energy is transmitted through the medium. The material of the medium is not transmitted.

Option (d) is incorrect because energy is transmitted through the medium.