Why do we wear cotton clothes in summer? 

Every option that is presented has to have its underlying facts examined. We shall discover the correct solution by ruling out the incorrect possibilities. To find the solution, we will also need to be aware of specific cotton qualities.
utilised formula: $H=m\times L$
We must first understand two crucial characteristics of cotton.
1. It is permeable. It implies that the cotton structure contains a lot of holes or open spaces.
2. Usually, it provides good heat insulation. So cotton doesn't transfer heat, then. It's because cotton is essentially packed with air, which is a poor heat conductor (usually).

Here, we must keep in mind that cotton, when filled with air, serves as the finest heat insulator. But during the heat, our bodies sweat a lot. Therefore, water will partially fill the holes in cotton clothing. Additionally, cotton's ability to act as insulation isn't very useful.
Conversely, perspiration gains access to atmospheric air as it enters the body. Additionally, air speeds up the process of perspiration evaporation (or any other liquid). A significant amount of heat is lost through evaporation, which comes from the body. The body therefore cools.
The amount of heat lost if one gram of perspiration evaporates is,
$H=m\times L$
The latent heat of vaporizationutilized is denoted by L.

Hence, the correct answer is option C.