Final answer:
The lost-update problem, unique to multiuser database systems, occurs when simultaneous transactions overwrite each other's data, causing consistency issues. Option C is correct.
Step-by-step explanation:
The lost-update problem is unique to a multiuser database processing system. In a scenario where multiple users are accessing and modifying the database concurrently, a lost-update occurs when two or more transactions read the same data and then each transaction writes a new value based on its read value, effectively overwriting each others' updates without knowing.
This can lead to inconsistent data and various transaction-related errors.
To prevent this, most database management systems implement locking mechanisms or use an optimistic concurrency control strategy to ensure data integrity. Locking mechanisms restrict other transactions from accessing the data until the first transaction is completed.
In contrast, optimistic concurrency control allows multiple transactions to proceed without locking, but only one will succeed when committing the changes. If there is a conflict, the later transactions must be redone with the updated data.