Ecosystems in the United States Experience Seasonality Because

Ecosystems in the United States experience seasonality because:

A) Earth is tilted with respect to the orbit around the sun.
B) the rotation of Earth causes a rhythmic circulation of Earth's atmosphere.
C) Earth rotates on it's axis relative to the sun.
D) there is a predictable seasonal solar activity cycle.
E) Earth is closer to the sun in summer and farther away in winter.