Final answer:
The speed of sound decreases with increased altitude due to decreased air density, which is a consequence of lower atmospheric pressure at higher elevations.
Step-by-step explanation:
The speed of sound in air is affected by several factors, including temperature, pressure, and the density of the medium. At higher altitudes, the air density decreases because the atmospheric pressure is lower than at sea level. Since the density of air affects how sound waves travel, the decreased air density at higher altitudes results in a decrease in the speed of sound. This is because sound waves are pressure waves, which means they move through the medium by causing the particles of the medium to vibrate. As the air becomes less dense, there are fewer molecules to facilitate the wave's propagation, and thus the wave travels more slowly. Therefore, the correct answer to how a rise in altitude affects the speed of sound transmitted through air is b) The speed of sound decreases due to decreased air density at higher altitudes.