The question is asking for the meaning of a word as used in the passage. Research the first sentence for context clues. This sentence introduces Melvil Dewey and the system that carries his name. Answer choice (B) clearly relates to the meaning of the sentence. There is no suggestion that the new system was the most important one or uniquely innovative (it could have been based on a previous system), making (A) and (C) incorrect. Nothing in the passage indicates that the Dewey Decimal System is logical and simple to use, as in (D).