If Central Bank A cares only about keeping the price level stable and Central Bank B cares only about keeping output at its natural level, then in response to an exogenous decrease in the velocity of money: A. both Central Bank A and Central Bank B should keep the quantity of money stable. B. Central Bank A should increase the quantity of money, whereas Central Bank B should keep it stable. C. Central Bank A should keep the quantity of money stable, whereas Central Bank B should increase it. D. both Central Bank A and Central Bank B should increase the quantity of money.