If the Earth being tilted on its rotating axis causes yearly temperature variations, then what causes yearly temperature variations?

Answer choices:
- 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    