The correct answer to your question is pretty simple! It is caused by Earth's B Rotation! You might get confused with C as well, but a revolution is when it rotates around the sun, when it does a complete loop around the Sun. A rotation is when it rotates around it's axis, and that is what causes day and night.
Hope I was able to help you out! If you have any more questions, please let me know and I will help you!
