Answer:
I think D it could maybe B
The correct choice is
D. 22 Hz and 42 Hz.
In fact, the beat frequency is given by the difference between the frequencies of the two waves:

In this problem, the beat frequency is
, therefore the only pair of frequencies that gives a difference equal to 20 Hz is
D. 22 Hz and 42 Hz.
during satellite motion we know that total energy is always conserved
so here we will have

here we know that


now at other position

now from above equation we have

now we have


so its kinetic energy will be 3500 MJ
Pseudoscience
Pseudoscience is made of up statements, beliefs or practices that claim to be scientific and factual but are not based in the scientific method.
The average density of the boat, including the steel and air, is less dense than 1.00 g/cm³.