The revolution of the earth around the sun alone is not enough for change of seasons. Had the axis of the earth been vertical, the sun would have been vertical at the same latitude throughout the year. Therefore the revolution of the earth and its inclination, both are necessary for the change of seasons.

Correct Option: C

The revolution of the earth around the sun alone is not enough for change of seasons. Had the axis of the earth been vertical, the sun would have been vertical at the same latitude throughout the year. Therefore the revolution of the earth and its inclination, both are necessary for the change of seasons.