The social critism in Upton Sinclair "the jungle" was a response to the working conditions faced by

The social criticism in Upton Sinclair's The Jungle was a response to the working conditions faced by immigrants.

Immigrants often have a difficult time getting accustomed to their new country and its culture, and the jobs are no different. Usually, the conditions they have to work under are quite difficult, which Sinclair is trying to convey in his work.