The answer is C or the baker uses 15 cups of cereal and 10 cups of marshmallow. This is because in the question it states that for every 4 cups of marshmallow there is 6 cups of cereal. So, 8 cups or marshmallow equals 12 cups of cereal and the two other cups needed are two which is half of four. So you just divide six in half and you get 15 cups or cereal and 10 cups of marshmallow. Sorry if that was confusing.