OFFICIAL EXPLANATION

The correct answers are B, F, and I. Answer Blank (i): Choice B, "tenable," means "based on reasoning and evidence, believable, defensible." It's the only option that contains the idea of credibility and defensibility, which would be necessary in a scientific field. Choice A, "desirable," means "worth having or valuable," and choice C, "worthwhile," means "valuable, useful, rewarding." Answer Blank (ii): Choice F, "specious," means "seemingly true, but actually false; not true" and fits the context. Both choice D, "delusory," and choice E, "deceptive," include an element of "intending to mislead" or "likely to mislead," which is not borne out in the passage.
Answer Blank (iii): Choice I, "repudiated," means "to reject something as untrue" and fits the context. Choice G, "reneged," means "to fail to act on a promise" and doesn't make sense. Choice H, "annulled," means "to declare invalid in a legal sense" and doesn't make sense.