To understand these SQL statements, the user needs to know how to query a database and sort the results in descending order based on a specific column.

The first SQL statement selects the last name, salary, and hire date columns from the EMPLOYEES table and orders the results by salary in descending order using the ORDER BY clause with the DESC keyword.

The second SQL statement is identical to the first one but uses the shorthand ORDER BY 2 DESC instead of explicitly specifying the salary column name.

Now let's go through each option and explain why it is right or wrong:

A. The two statements produce identical results: This option is correct. Both SQL statements select the same columns and sort the results in the same descending order based on the salary column. The shorthand ORDER BY 2 DESC in the second statement refers to the second column in the SELECT clause, which is the salary column.

B. The second statement returns a syntax error: This option is incorrect. The second SQL statement is a valid syntax and produces the same results as the first one.

C. There is no need to specify DESC because the results are sorted in descending order by default: This option is incorrect. SQL sorts the results in ascending order by default, so the DESC keyword is needed to sort the results in descending order.

D. The two statements can be made to produce identical results by adding a column alias for the salary column in the second SQL statement: This option is incorrect. Adding a column alias does not change the way the ORDER BY clause works. It only renames the column in the result set.

The Answer is: A