Earth has seasons primarily due to its
a. tilt
b. rate of rotation
c. rate of revolution
d. distance from the sun

Earth has seasons primarily due to its tilt of roughly 23 degrees, since this allows for sunlight to hit the Earth in different ways as the Earth rotates around the Sun. The distance of this rotation remains fairly constant. 

In the midwest because it has more moderate climate than the north or south west which makes farming far easier.