The correct way to compute the total annual compensation, which includes the monthly salary and the monthly commission (if any), is:
* Option C: SELECT last_name, (monthly_salary * 12) + (monthly_salary * 12 * NVL(monthly_commission_pct, 0)) AS annual_comp FROM employees;
* This statement takes the monthly salary and multiplies it by 12 to get the annual salary, and then adds the annual commission which is the monthly salary multiplied by the commission percentage (if any, else 0) and then by 12.
Options A, B, and D are incorrect because:
* Option A: Does not handle the case where the commission percentage is NULL which would result in NULL for the entire expression when added to the monthly salary.
* Option B: Does not consider that the commission percentage might be NULL which could lead to incorrect calculations (or NULL values if commission is NULL).
* Option D: Incorrectly adds the monthly commission percentage directly to the annual salary without considering that the percentage needs to be applied to the salary.