A monster cookie recipe calls for 2 cups of chocolate chips, 1 cup of nuts and 3 cups of oatmeal. Mary has 9 cups each of oatmeal, chocolate chips, and nuts. If Mary repeats this exact recipe as many times as possible, how many cups of chocolate chips will she use?
A. 2 cups
B. 4 cups
C. 6 cups
D. 8 cups