When land has been overfarmed or overgrazed, occurs.
a. wasteland
b. deforestation
c. desertification
d. underdevelopment

The best option is C. desertification.

When land has been over farmed or overgrazed , desertification occurs.

Desertification is said to be a process  of degradation of land whereby land that was previously biologically productive is changed into a barren, unproductive land.

Desertification can be brought about by poor use  and destruction of natural resources such forest and natural vegetation. Such include:

1. Excessive tree felling or cutting

2. Unsustainable farming practices  which lead to loss of soil fertility.

3. Removal of vegetation cover.

4. overgrazing.

5. Uncontrolled fuel wood gathering  or collection.