Final answer:
A cardholder who forgot their ATM PIN can reset it online, through customer service, or in some cases, at an ATM itself; hence, all the provided options are correct depending on the bank's available services.
Step-by-step explanation:
If a cardholder forgot their PIN and cannot use the ATM, there are several steps they can take to reset their PIN. Option (a) Online, is a common method where the cardholder can go to the bank's website or mobile app, and after going through the necessary identification and security questions, they can set a new PIN. Option (b) Through Customer Service, the cardholder can call the bank's customer service hotline, verify their identity, and receive instructions or assistance in resetting their PIN. Option (c) At an ATM, is less likely as it typically requires the cardholder to enter their existing PIN to change it to a new one. However, some banks offer a service where one can reset their PIN using a temporary code provided by customer service. Therefore, the correct answer is (d) All of the above, as all these methods can be employed to reset a forgotten ATM PIN, depending on what services the bank offers.