Question

which is a cause of desertification?
farming
creating reservoirs
overgrazing
driving motor vehicles

Explanation:

Desertification is the degradation of land in dry regions. Overgrazing, where livestock eat vegetation faster than it can regrow, removes plant cover that holds soil in place, leading to soil erosion and desertification. Sustainable farming does not cause desertification, reservoirs can support water access, and motor vehicle driving has minimal direct link to widespread desertification.

Answer:

overgrazing