why is one side of the moon called the dark side of the moon

Question

is it 

A) The moon is in earths shadow

B) The moon both rotates on its axis and revolves around earth every 28 days

C) Earth is in the moons shadow

Answer 1

As I understand it, the Earth exerts a gravitational pull on the Moon such that it affects the Moon's rotational speed on its axis, with the result that the Moon rotates precisely slowly enough to keep one hemisphere of the moon, what we commonly know as the "the man in the Moon" due to its suggestion of a human face, always facing the Earth, hence it's the only side of the moon we ever observe in the sky. The other hemisphere is therefore called "the dark side of the moon" because we never see it illuminated by reflected sunlight (or Earth light), even though that hemisphere is very often in the direct path of the Sun's light.

 

So I guess the best answer of the choices you give is (B) since it mentions the axial rotation of the moon, but it's rather lacking since there's no mention of the affect of this on the positioning of both "sides" of the moon relative to the Earth. (A) is true only when there's a lunar eclipse, i.e., when the moon's orbit carries it directly behind the Earth in line with the Sun, and (C) describes what happens in a solar eclipse, i.e. when the moon transits across the Sun and thus "casts a shadow" on the Earth.