If 12 coulombs of electric charge pass a point in 4.0 seconds, the current is
A) 8.0 amperes
B) 16 amperes
C) 3.0 amperes
D) 48 amperes

The rocks expand when there hot/warm  and contract when they are cold.

The anwser is: wave a has a greater pitch and frequency.

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.