Shelter belts prevent topsoil loss because

they conform to the shape of hills
tree roots hold soil
trees act as windbreaks
strips are plowed on land

The answer to the question above is letter "C" "the trees act as windbreakers".

Shelter belts prevent topsoil loss because the trees act as windbreakers. Planting more trees and preservation of the environment will result in a less damage environment. The topsoil soil will be held in place.

C. gemstones they are the only non metallic mineral from the list.