Answer:
A
Explanation:
The Earth rotates on a tilted axis. Since the Earth also moves around the sun, one part of its face will be exposed the sun's light, while the other part will be in darkness.
Because the Earth spins, for a certain number of hours, one face will be exposed to the sun, so that's day. However, after spinning for a while, that face will then be turned away from the sun, and will experience darkness, which is night.
Thus, day and night are caused by the Earth's rotation on its axis.
Hope this helps!
