Will give brainliest

The answer is C.

They were doing desertification

Explanation: Desertification: The process by which land becomes more dry until it turns into a desert.

People who live in the sahel have to adapt to their enviroment. They mostly farm plants called millet and sorghum. These are the few plants that can grow here because it is marginal land, land that isn't good for farming. The desertifiction forces farmers to move their fields alot, which is called shifting agriculture.