How would an increase in the required reserve ratio affect banks' ability to create money?

a. Banks will be able to create more money because of the decrease in excess reserves.

b. Banks will be able to create more money because of the increase in the demand deposit multiplier.

c. It will have no effect on banks' ability to create money. 

d. It will reduce banks' ability to create money by forcing them to hold more reserves.

e. It will reduce the banks' ability to create money by increasing excess reserves.