To solve this question, the user needs to have knowledge about PL/SQL syntax, specifically about creating stored procedures, and error handling using exceptions.
Option A is incorrect. The procedure does not have any syntax errors; there is no errant comma.
Option B is incorrect. The STATS_EXIST_EXCEPTION is not a number or a variable that needs to be declared. It is a user-defined exception that will be raised in case of an exception with the specified condition.
Option C is correct. The STATS_EXIST_EXCEPTION is not declared as an exception, which will cause an error during compilation of the stored procedure. The correct way of declaring a user-defined exception is as follows:
EXCEPTION
WHEN THEN
-- handle the exception
Option D is incorrect. PL/SQL allows users to define their own exceptions using the EXCEPTION keyword. Predefined exceptions are not the only exceptions allowed in the EXCEPTION section.
Therefore, the correct answer is:
The Answer is: C. The STATS_EXIST_EXCEPTION has not been declared as an exception.