Garbage Collectors Are Paid a Higher Wage Than Many Others

Garbage collectors are paid a higher wage than many others with comparable skills because:

A) there are dangers associated with collecting trash.
B) garbage collectors work much longer hours on average than do those in other jobs.
C) there is unpleasantness associated with trash collection.
D) garbage collectors possess skills that are in relatively high demand
E) it takes a considerably longer time to acquire the skills.