What is desertification? how are nomads and drought related to this process

The process of desertification refers to the degradation of land. In simple words, it means changing of a fertile land into an infertile one. It has become one of the major issue in today's world. It is mainly caused due to the lack of rainfall, climate change, deforestation, overgrazing. The consequences of desertification is the occurrence of drought.  

Drought is one of the common type of disaster that can have serious impact on the lives of planets. Due to this, a large number of people have to shift their places in order to search for food and to live. These people who migrate from one place to another, having no fixed location are considered as the nomads.

So, in one way, it can be concluded that droughts are responsible for the loss of habitat and people have to migrate from one place to another like the nomadic people in order to survive.

i think it would be b. tissue because an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.