Answer:
B. His job performance is lower than that of most other employees.
Explanation:
If it said the Ron is not perfect then it means that he do not perform as good as what is at-least expected from him.
This is because he is very dedicated to his work, but even after that he is not able to deliver what is expected from him. Maybe because all other employees deliver what is desired from them.
Accordingly he performs lower than most of the employees and that is the important reason provided he is not the perfect employee.
Thus, he is performing lower than most of the employees.