Earth orbiting the Sun causes seasons to change, and seasons are caused by the tilt of the axis relative to the planet's orbit. Given these facts, what causes earth's seasons among 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     