16) Social engineering is A) verifying credit card validity; buying and selling stolen credit cards. B) inserting a sleeve into an ATM so that it will not eject the victim's card, pretending to help the victim as a means of obtaining his PIN, and using the card and PIN to drain the account. C) a technique that tricks a person into disclosing confidential information. D) changing data before, during, or after it is entered into the system in order to delete, alter, or add key system data.