Answer:
Option (1)
Step-by-step explanation:
Desertification refers to the process of transformation of a land area which is productive in nature, into a desert. It leads to the reduction or elimination of the vegetation-covered area. The Sahara desert also is formed and is constantly expanding at a faster rate. According to the researchers, it has been observed that it is expanding by 10% every century. The cause of this desertification includes both natural processes such as climate and human activities.
In the given question, the desertification of Sahara refers to the expansion of the Sahara desert.
Thus, the correct answer is option (1).