What is true about them?

Evaluate these two SQL statements:
SELECT last_name, salary, hire_date FROM EMPLOYEES ORDER BY salary DESC;
SELECT last_name, salary, hire_date FROM EMPLOYEES ORDER BY 2 DESC;
What is true about them?

A.
The two statements produce identical results.

B.
The second statement returns a syntax error.

C.
There is no need to specify DESC because the results are sorted in descending order by
default.

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.

Explanation:
the two statement produce identical results as ORDER BY 2 will take
the second column as sorting column.
Incorrect answer:
Bthere is no syntax error
Cresult are sorted in ascending order by default
DORDER BY 2 will take the second column as sorting column.
Refer: Introduction to Oracle9i: SQL, Oracle University Study Guide, 2-22