In Africa, allowing livestock to feed for too long in the same area, planting on the same land over and over, and cutting down forests can all lead to
A. overgrazing
B. desertification
C. overfarming
D. deforestation

overfarming, or deforestation

Explanation:

Overfarming means you farm too much, after the environment has been cut down, and deforestation means that people keep cutting down all forests.

You can choose either one. Both of them make sense

d. i., ii., iii., and iv.