To answer this question, you need to understand the scope of variables in SQL*Plus.
Option A) Until the database is shut down - This option is incorrect. Variables in SQL*Plus are not persistent and do not persist beyond the current session or statement. They are not retained when the database is shut down.
Option B) Until the instance is shut down - This option is incorrect. Similar to option A, variables in SQL*Plus are not persistent and do not persist beyond the current session or statement. They are not retained when the instance is shut down.
Option C) Until the statement completes - This option is correct. Variables in SQL*Plus are only valid for the duration of the current statement. Once the statement is completed, the variables are no longer available.
Option D) Until the session completes - This option is incorrect. Variables in SQL*Plus are only valid within the current session. Once the session is terminated, the variables are lost.
The correct answer is C) Until the statement completes. This option is correct because variables in SQL*Plus are only available for the duration of the current statement. Once the statement is completed, the variables are no longer accessible.