The correct answer is "mold".
Depending on the type of cheese, each would contain, respectively, one of the following two types of molds: Penicillium roqueforti, typically found in blue cheeses (such as: Stilton, Roquefort, and Gorgonzola) and Penicillium camemberti, present in the surface of mold-ripened cheeses (for example, Camembert and Brie).