Question

letters a, b, c, and d in the diagram below represent four positions of the moon in its orbit around earth.
(diagram: suns rays coming from left, earth in center with a shaded half, moon at positions a, b, c, d in orbit around earth, each with a shaded portion. not drawn to scale)
at which moon position would a person on earth see the entire lighted half of the moon (full - moon phase)?
a a
b b
c c
d d

Explanation:

A full moon occurs when the entire face of the Moon facing Earth is illuminated by the Sun. At position B, the Moon is opposite the Sun relative to Earth, so the side of the Moon facing Earth is fully lit by the Sun's rays. Positions A, C, and D show partial illumination (quarter or crescent phases).

Answer:

B. B