Which of the following systems rewards an employee based on the length of service the employee has had with the organization?

The answer would be Seniority based Reward System

Explanation:

In a seniority based Reward System, employees are rewarded on the basis of the length of the service they had with the organization. This type of reward system is not appreciated mostly by employees, because in this type of system, employees with high performance are not recognized early unless they have a long period of service with the organization. Performance based rewards are highly appreciated by the employees and are practiced by organizations now a days.