The positions of the constellations appear to change throughout the year because
a. earth revolves around the moon
b. earth revolves around the sun
c. the constellations revolve around earth
d. the sun revolves around earth

The correct answer is - b. Earth revolves around the Sun.

Because of the revolving of the Earth around the Sun, which to put it simple represents an ellipsoid imaginary track by which the Earth moves around the Sun in 365 days because of the gravitational pull from the Sun, the constellations seem to change positions throughout the year. Actually the constellations do not change their positions, their positions change from our standpoint because the Earth changes its positions so the constellations appear to us on different parts of the sky in different periods of the year.