The research described in the passage is primarily concerned with answering which of the f

A．How can researchers reproduce the useful effects of hypnosis in a medical setting？

B．How are experiments devoted to disproving the "vivid imagination" objection to hypnosis different from those devoted to disproving the "placebo effect" thesis？

C．What research guarantees the reality of the effects that hypnosis has on brain activity, and what is their causal mechanism？

D．What technical advances have permitted researchers to reject skeptical explanations of the phenomenon of hypnosis？

E．What relationship does brain activity have to the subjective experience of the hypnosis phenomenon？