In the passage, the author is primarily concerned with

A． identifying the differences between science and pseudo-science as they relate to skepticism
B． stressing the importance of employing the scientific method to assuage skeptics
C． proposing a new scientific approach which answers the objections presented by skepticism
D． offering a model of skepticism that is both useful to science and avoids the pitfalls of relativism
E． explaining the difference between the assumptions made by relativists and those made by skeptics