Why did Gustave Courbet start the 19th-century art movement known as Realism?

A. He was moved by working-class struggles and the realities of poor people.

B. He was tired of painting outdoors and wanted to paint inside in a studio.

C. The church was no longer hiring artists to paint, so he had to find another way to make a living.

D. The French government hired him to revolutionize propaganda in art.