Why is one side of the moon called "the dark side of the moon"

A. The moon both rotates on its axis and revolves around Earth every 28 days.

B. The moon is in Earth's shadow

C. Earth is in the moon's shadow

The answer to this question would be: A. The moon both rotates on its axis and revolves around Earth every 28 days.

The moon rotates and revolves in the same rate of 28 days. That means the side that we can see from earth would be same all around the year. That also goes to the side which we can't see, and that side is called "dark side of the moon" because we can't see it.