Context: Figure: Oglala National Grassland.
Oglala National Grassland is a prairie grassland ecosystem in northwestern Nebraska.
Which better describes the Oglala National Grassland ecosystem?
A. It has hot summers and cool winters. It also has soil that is rich in nutrients.
B. It has a small amount of rain. It also has dry, thin soil.
Determine the correct option from the provided choices and reply with its corresponding letter.

A