OE

D

The blank refers to something described as scientific. The clue is must observe every detail, no matter how small and seemingly unimportant. The transition word actually indicates that the blank refers to something that is “important,” so use that as a word for the blank. Choices (A), (B), (C), and (E)— recessions, obstructions, incapacities, dissolutions— can be eliminated because they do not match “important,” so the correct answer is (D), breakthroughs.