You are developing a bonus report for the payroll application to calculate and display the bonus issue to each envelope. Employees with a salary of less than 50000$ earn a bonus of 15% and the employees who earn 50000$ or more earn out 10% bonus. Which type of trigger would you use to conditionally assign a bonus percentage?（）

• A、Report level trigger. 
• B、Group filter. 
• C、Format trigger. 
• D、None of the above.