Which of the following methods of validating PINs seems to result in the fewest control problems?

a. Allow only a small number of PIN entry attempts, close the account after the limit has been reached, and retain the card

b. Allow a reasonable number of PIN entry attempts, close the account after the limit has been reached, but do not retain the card

c. Allow a reasonable number of PIN entry attempts, close the account after the limit has been reached, and retain the card

d. Allow a small number of PIN entry attempts, do not close the account after the limit has been reached, but retain the card used to initiate the PIN entry