If one sound wave has twice the amplitude of another the first sound is

occurs when path-length difference is:

Δr=mlambda and m=0,1,2,3...

Explanation:

I think thats the answer.

the answer is neither ball has a charge.

because if they were both positively charged, they will repel each other.

if they were positively and negatively charged, they will seek.

i am pretty sure it is c because when people are closer together, they cannot move as freely. picture being in a mostly full elevator, for instance. the people are right next to you, and you can barely move.