The speed of a mechanical wave through a medium depends on the type of medium. It also depends on the type of mechanical wave. Which statement is true? A. All waves travel at the same speed through any medium.
B. All waves travel at the same speed if no medium is present.
C. Electromagnetic waves require a medium, but mechanical waves do not.
D. Mechanical waves require a medium, but electromagnetic waves do not.

samuel gompers was an extremely important person in the american labor movement, being him an employee all his life he devoted himself to fight for the rights of his pairs, he believed they all had the right to have better thing and that they all were working for them but the factory workers were greedy, ambitions and socialist people for him who he didn't have a good concept of.

he gave so many speeches and led so many strikes and protest to fight for equality which he considered employers didn't want to accept, so he had an absolutely negative opinion of them.

the gas pressure p, gas volume v, and gas temperature t are given in the formula:   pv=nrt,

r is the gas constant, and n is the number of gas moles.

if the container is cooled and remains under atmospheric pressure, where r is a constant that does not change, the volume of the container remains the same, the conclusion is drawn that, with all other values ​​unchanged, the number of gas moles n, is decreases.

the right answer is a.