Postal Service Practice Exam

A credit card is considered valid primarily through the presence of a signature. When a cardholder signs the back of their credit card, it serves as a verification method that aligns with the details on the card and the credit card issuer's records. This signature acts as a form of authentication and ensures that the person using the card is indeed the authorized cardholder.

While other options like a PIN number or forms of identification can enhance security during transactions, they are not universally required for the validity of a credit card. Many transactions can occur without a PIN, particularly in situations such as swipe payments. Therefore, the signature remains a critical component in affirming the legitimacy of the card’s use. The requirement for a contact number is not standard for establishing a credit card’s validity either, as it is more related to customer service or account management rather than transaction authorization.