Seasonal changes occur because of

a. Earth s tilt.

b. Earth s shape.

c. the distance between Earth and the moon.

d. the time of year.

Seasonal changes refer for example to the fact that in the Norther hemisphere it's colder in December than in June. This is because the Earth's axis is tilted in a way that brings the Western Hemisphere closer to the sun in July and further from the Sun in December.

The correct answer is: Earth is tilt.