Final answer:
A use case diagram should be drawn to represent the interaction between the bank user and the ATM, as it clearly illustrates the relationship between users and the system functions.
Step-by-step explanation:
To represent the interaction between the bank user and the ATM, a use case diagram should be drawn. This type of diagram shows the relationship between users (or actors) and the different use cases, which are the functions or services provided by the system. In this scenario, the actor is the bank user, and the use cases could include withdrawing cash, checking account balance, depositing funds, and so on. A use case diagram is helpful in understanding the external user perspective of system functionalities without detailing the internal workings of the system. It's especially useful early in the development process when system behaviors and interactions with users are being defined.