First body:

Second body:

From description of the task we have:
Answer:
OPTION D (The waves will sometimes get very high and very low) is the answer.
Explanation:
Wavelength = velocity ÷ frequency
As the frequency which measures the number of waves per unit of time is inversely proportional to the wavelength, point X which lies between two sources, and one source is shorter than another, the wave heights at point x will vary as the distances from point X vary too. This means that waves at point X depending on the wave type and source will get very high at times and very low.
It's pretty simple. When air is leaking out of a tire, like a tiny hole or something, the pressure in the tire decreases, because without air in the tire, there is no pressure.
Answer: The elevator must be accelerating.
Explanation:
As the tension force is opposing to the the force of gravity on the load which is hung vertically, and the tension force can adopt any value in order to comply with Newton's 2nd law, if the tension force is less than the force due to gravity, this means that all system is not in equilibrium, so it must be accelerating.
If we assume that the downward is the positive direction, we can write:
mg - T = ma
If T = 0.9 mg, ⇒ mg (1-0.9) =0.1 mg = m a ⇒a = 0.1 g , in downward direction.