Fact 1: Earth orbiting the Sun causes seasons to change.

Fact 2: Days and hours change seasonally.

Given the two facts above, answer the question "What causes days to change?" with the following options: 
- Space travel
 - recovery time from fatigue
 - Earth orbiting the Sun
 - sunlight
 - earthquakes
 - Solar energy
 - prolonged thirst
 - global warming


 

   Earth orbiting the Sun      