Answer:A)Smart-card PINs
Explanation: A pin is the defines as the personal identification number that is allotted to the smart card uniquely that is no other smart can have same number.This number is only known by the smart card holder only.
This number is important because it works for the unlocking of the data that is securely stored and by entering the pin ,it can be decoded.Thus, the other given options are incorrect because they don't use enumeration to hide the data .Thus the correct option is option (A)