an organization creates an audit trail of when employees enter the building by having them use a key card to release a magnetic lock. a database record who enters when. which of the following reduces the risk that the audit trail is incomplete?

a. installing a redundant character check for card verification

b. policy prohibiting employees form allowing other employees to enter without using their own card.

c. have the back door operate via physical key lock and providing the key only to certain employee

d. installing the key card matching database near the door