The answer is
C. periodic fluctuations in the intensity if sound waves.
In uniform motion, the path is a straight line, and the object r moving along it at a constant speed.
Answer:
it appears to be farther away than it actually is, and therefore smaller then the object itself.
The vibrations are analyze and turned into sounds in you ear
The second one, air is a poor conductor. If it weren't it wouldn't be used as such in construction. It's not the best insulator, but is quite efficient, and much cheaper to include a layer of air inside a wall than to add additional layers of asbestos :)