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

Fact 2: Seasons are caused by the tilt of the axis relative to the planet's orbit.

Given the two facts above, answer the question "What causes earth's seasons?" with the following options: 
- principals of aerodynamics
 - Physical weathering
 - floods
 - the tilt of the planet
 - an external framework
 - dry conditions
 - axis rotation
 - relative location


 

    the tilt of the planet     