What is the angle between the earth, sun and the moon on a full moon day?
A) 180 degree
B) 150 degree
C) 170 degree
D) None of the above

Hint: Full Moon occurs when the Moon has moved in its orbit so that Earth is “between” the Moon and the Sun. Between the new and full Moon, the amount of Moon we see grows — or waxes from its right side toward its left side

Complete answer:
As it orbits the Sun, the Earth rotates on its axis. A complete rotation takes roughly 24 hours per day. The Sun appears to rise in the east and set in the west due to this counterclockwise motion from west to east.The earth revolves around the sun in an elliptical orbit. As the Earth revolves around the Sun, the Moon rotates on its axis and revolves around it.

Option A) – This option is correct because the lines connecting the earth, the sun, and the moon form a 180-degree angle on each full moon day. Even so, the sun, Earth, and Moon may not be in a straight line in the same plane on every new or full moon day. So 180 degrees is correct.
Option B) – This option is not correct with regard to what is asked in the question because this angle represents the opposite phase of one of the moon's phases, waxing gibbous. During the waxing gibbous phase, the angle changes from 91° to 179°, representing the 150° angle in between.
Option C) – This option is also incorrect because on full moon day the angle between the earth, sun and the moon is 180 degree, and the angle 170 degree belongs to the other stage of the moon which is the waxing gibbous stage, hence, this option is wrong.
Option D) – This can’t be correct because at least one should be the right option out of the 4 options. Therefore, 180 degree is the correct answer.

Therefore the correct answer is option ‘A’.

Note: The Moon is divided into eight phases: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Third Quarter, Waxing Crescent, and New Moon again. These eight moon phases are further divided into four primary phases and four intermediate phases. The primary phases are the major alignment positions of the Earth-Moon-Sun system's geometry. These are the New Moon (0°/360°), First Quarter (90°), Full Moon (180°), and Third Quarter (270°) alignments.