Agar is added to Broth medium:

Ans. B. To make the medium solida. Broth media can be made solid by adding agar, a gel like polysaccharide extracted from red algae,b. Broth with about 1.5% agar added will be liquid when heated, but solid at room temperature, making it easy to pour into a vessel, such as a Petri dish or test tube when hot.c. The solution then becomes solid once cooled.