If Bob Withdraws $100 from His Checking Account and the Reserve

If Bob withdraws $100 from his checking account and the reserve requirement is 10 percent, then:

A) the money supply can decrease by as much as $1000, if banks hold some excess reserves.
B) the money supply can increase by as much as $1000, if banks hold no excess reserves.
C) the money supply can decrease by as much as $100, if banks hold some excess reserves.
D) the money supply can decrease by as much as $1000, if banks hold no excess reserves.