What causes the phases of the Moon?

A) the Earth's shadow obscures different amounts of the Moon during the year
B) the Earth's shadow obscures different amounts of the Moon over 28 days
C) the relative positions of the Sun, Moon, and Earth cause us to see different amounts of the Moon's lighted side
D) a partial eclipse causes the lighted part of the moon to grow and shrink over time

Phases Of The Moon

The monthly cycle of the Moon in which its illumination changes on a regular schedule, going from completely dark to fully lit and back again.

Earth's Shadow

The shadow that the Earth casts into space, observable during lunar eclipses when the moon passes through it.

Lighted Side

The part of a celestial body, like the Earth or the Moon, that is illuminated by the sun at any given time.