Final answer:
Riley's action of transferring $50 each month using online access is an example of B)an electronic funds transfer (EFT), which is an electronic transaction between bank accounts.
Step-by-step explanation:
The scenario where Riley moves $50 each month from her checking account to her savings account using online access illustrates B. an electronic funds transfer. An electronic funds transfer (EFT) allows money to be transferred from one account to another electronically without the need for a physical exchange of cash. EFT is a common method used for bill payments, direct deposits, and when transferring money between one's own bank accounts, as in Riley's case. This is distinct from using an automatic teller machine (ATM), which is a physical device used to withdraw cash, deposit funds, or perform other banking transactions.