For the Moon to Appear as a Crescent Shape to an Observer

Multiple Choice

For the Moon to appear as a crescent shape to an observer, the

A) observer must be closer to the Sun than to the Moon.
B) observer must be on the opposite side of the Sun from the Moon.
C) Moon must be closer to the Sun than the observer is and somewhere between the Sun and the observer.
D) observer and the Moon must be at equal distances from the Sun.