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

Fact 2: Seasons on the earth are due to the tilt of the earth's axis.

Given the two facts above, answer the question "What causes seasons to change?" with the following options: 
- Time and energy
 - gravity
 - orbital tilt
 - clouds
 - global warming
 - weather
 - climate
 - an object


 

   orbital tilt      