Yep, B is definitely correct, and your reasoning is right too.
For the explosion, the noise is sound, which is also a pressure wave. This wave is created by the force of the explosion (expanding gases), and travels outwards from the explosion. You hear the sound when the pressure wave reaches you, and once the wave has passed, the noise stops (it will keep traveling and the energy of the wave will eventually be completely absorbed by the medium and other objects).