Nitrogen dioxide can be made with the reaction of nitrogen monoxide and oxygen. Assuming that the reaction is at equilibrium, what effect would a decrease in the concentration of NO_2 have on the equilibrium position once the equilibrium is reestablished?

A. An increase in the amount of begin mathsize 14px style NO subscript 2 end style.

B. An increase in the amount of begin mathsize 14px style straight O subscript 2 end style.

C. No change in the amount of begin mathsize 14px style straight O subscript 2 end style.

D. An increase in the amount of NO.