How does the Conservation Reserve Program (CRP) try to protect soil for future agriculture?

a. The CRP provides grants to farmers willing to use contour farming.
b. The CRP is a policy that makes it illegal to plant the same crop on a piece of land three years in a row.
c. The CRP imposes financial penalties on farmers who do not employ shelterbelts in areas prone to wind erosion.
d. The CRP pays farmers not to grow crops on land that is not very well suited for crop production.