Fact 1: The Earth being tilted on its rotating axis causes seasons.

Fact 2: Latitude and season cause temperature variations.

Given the two facts above, answer the question "What causes yearly temperature variations?" with the following options: 
- earth's rotation
 - scattered light
 - earth's bend on rotating axis
 - exposure to cold
 - depress neuronal excitability
 - earth's tilt on rotating axis
 - wind and erosion
 - earth's tilt on rotating half


 

      earth's tilt on rotating axis   