What Does the Empirical Evidence Regarding Compensating Differentials Tend to Reveal

What does the empirical evidence regarding compensating differentials tend to reveal?

A) They do exist in situations of job safety and work hazards.
B) There is evidence of the existence of both positive and negative differentials for a wide range of job amenities and disamenities.
C) It is hard to find the evidence to support the theory of compensating differentials.
D) They do not exist.
E) There is evidence that they exist, but the methodology is so fraught with pitfalls that the evidence is not deemed to be credible.