Two buses ‘A’ and ‘B’ are moving in the same direction with the velocities 30m/s and 40m/s respectively. Find the relative velocity of the bus ‘A’ with respect to the bus ‘B’. Calculate the relative displacement between them after 4 minutes?

Ibelieve the answer is d. macula  hope my answer has you : )

Answerit decreases;

Sounds propagates through some kind of medium. usually it's air, but it goes just as well through solid objects like walls, windows etc. a soundwave will compress the (air)molecules in front of it, and if this increased density wave hits your ears, you register it as sound. solid objects like walls are a lot denser than air, this means that they will damp a wave, but also carry it easier.