Final answer:
Depositing cash into a savings account is the transaction that must be done in person compared to the other options, as it involves physical currency that cannot be transferred electronically.
Step-by-step explanation:
The transaction that must occur in person rather than through online banking is Depositing cash into a savings account. While technology has made many banking activities convenient, certain transactions still require physical interaction. For instance, depositing physical currency into a bank account typically necessitates a visit to the bank or an ATM. In contrast, depositing a check can be done virtually through mobile deposit features provided by many banking apps, making payments on mortgages can be scheduled and completed online, and ordering new checks for a checking account is often just a matter of a few clicks on the bank's website or app.