You are presented with the question "What causes day and night?" and the following answer choices: 
- chemical messengers
 - The moon
 - The ocean's waves
 - chemical reaction
 - Revolution around the sun
 - The clock on the wall
 - Evaporation of water
 - Basic units of the plant body.

Now knowing that aplanet rotating causes cycles of day and night on that planet and the gravitational pull of the major planets alters the orbital period from revolution to revolution, choose the best answer.


 

     Revolution around the sun    