(A) susceptible to , (E) a salubrious, (G) act as a tonic

The phrase at the end of the passage is useful because it indicates that studies have connected increased dosage with increased harm. The word “however” creates a shift to this assertion, thus the portion of the passage before the assertion must imply the opposite—that the radiation has a positive effect. Blank (i) can be susceptible to (vulnerable to), since if the doses make people less susceptible to something, the effect is positive. Blank (ii) continues this direction, so salubrious (healthful) would fit, and blank (iii) is being criticized by the passage’s argument, so it could be acts as a tonic (aid).

(C) overweening, (D) conceits, (I) chagrined

If the scientist is “puffed up,” “callow” (inexperienced), and if he “trumpeted” his results, his pride could be described as overweening (arrogant). If his colleagues “cringed,” the paper could have self-congratulatory conceits (unduly high self-opinions). The phrase “even more” indicates an increase in a description’s intensity, so chagrined (dismayed) would logically be an increase from the colleagues’ initial cringing

(B) nonplussed by, (D) a shrewd

The word “though” creates a shift from blank (i) to “soon recovered,” so blank (i) could be nonplussed (perplexed). Blank (ii), then, needs to contrast with the general’s initial confusion, so designing a shrewd (cunning) plan would create such a contrast

(A) truculence, (D) assailed

A clue for blank (i) is provided by the description of the cheetah as eager to fight; truculence (disposed to fight) fits. This description is then said to lead to the cheetah charging “too quickly.”

(E) iteration

A clue for the blank is provided by “repetition,” which implies that the fractal describes via iteration (repetition).

(D) loquacious

If the emissary used a barrage of verbiage (excessive wordiness) to divert, then he couldhave been described as loquacious (talkative).

(C) enormity, (E) cognizant of, (G) reviled

The scientist knew he would be condemned, and enormity (excessive wickedness)would fit blank (i) if he realized the enormity only after seeing that the offspring were “twisted” and “suffering.” Reviled (hated) fits blank (iii): the scientist was already condemned, so “even more” signifies a higher degree of that condemnation. Logically, if the public was cognizant (aware) of the experiments’ depravity (having low moral values), they would revile him.

(C) fanciful, (D) flabberagasted, (H) homage to

If the magician is daydreaming about his entire audience being spellbound, those daydreams could be described as fanciful (whimsical; imaginary). If he is “not immune” to those daydreams, he could be described as susceptible to them. Then the word “nevertheless” creates a shift from the expected result; therefore, blank (ii) could be flabbergasted (astounded), since one would expect the magician to be used to fantasizing about his effect. If
the “throngs of admirers” are prostrate (lying face down), they could be so in homage (public respect) to him.

(C) quiescence, (E) short-lived

If a butterfly had quiescence (the quality of being still), the entomologist might have time to sketch it. Blank (ii) could be short-lived because of the shift that the word “though” creates;
the shift is from “short-lived” to “ample (plentiful) time.”

(C) grandiloquent, (D) dissuaded

The word “thought” signifies a shift from “skilled,” so blank (i) must be negative, and since the speaker is criticized for bombast (pompousness), then he could be grandiloquent (pompous; self-important). This unflattering self-importance would understandably have dissuaded (deterred) many of his followers.

(E) dulcet

If the 12th graders have “melodies,” which “drifted pleasingly,” then those melodies could be described as dulcet (melodious; pleasing).

(A) bucolic

The descriptive phrasing after the semicolon provides clues. “Epitome of politeness and composure” is similar to urbane (polite; sophisticated), and “rustic” and “rural” fit bucolic (rustic; simple).