To answer this question, you need to understand transaction control in database management systems.
Option A) Lock - This option is correct because locks are used to prevent more than one user from updating data in a table simultaneously. Locks are acquired on the table or specific rows and are released after the transaction is complete.
Option B) Commit - This option is incorrect because the commit operation is used to permanently save the changes made during a transaction. It does not prevent multiple users from updating data simultaneously.
Option C) Rollback - This option is incorrect because the rollback operation is used to undo the changes made during a transaction and restore the database to its previous state. It does not prevent multiple users from updating data simultaneously.
Option D) Savepoint - This option is incorrect because savepoints are used to mark a specific point within a transaction to which it can be rolled back. It does not prevent multiple users from updating data simultaneously.
The correct answer is A) Lock. This option is correct because locks are used to prevent more than one user from updating data in a table simultaneously.