A bank has a system that manages financial transactions.

Isolation. See course material:

o concurrent transactions cannot interfere with one another, and must result in a consistent database state.

o For example, while the transaction to transfer funds from one account to another is in-process, another transaction that checks the balance of these accounts must return consistent results - the balance-checking transaction can't retrieve a value for one account that reflects the balance before the transfer, and a value for the other account that reflects the balance after the transfer.