The highest-ranking detectives in the city s police department are als

The highest-ranking detectives in the city's police department are also the most adept at solving crimes. Yet in each of the past ten years, the average success rate for the city's highest-ranking detectives in solving criminal cases has been no higher than the average success rate for its lowest-ranking detectives.

Which one of the following, if true, most helps to resolve the apparent paradox?

(A) The detectives who have the highest success rate in solving criminal cases are those who have worked as detectives the longest.

(B) It generally takes at least ten years for a detective to rise from the lowest to the highest ranks of the city's detective force.

(C) Those detectives in the police department who are the most adept at solving criminal cases are also those most likely to remain in the police department.

(D) The police department generally gives the criminal cases that it expects to be the easiest to solve to its lowest-ranking detectives.

(E) None of the lowest-ranking detectives in the police department had experience in solving criminal cases prior to joining the police department.