GRE General Test: SE-705560 GRE Sentence Equivalence

Though one cannot say that Michelangelo was impractical designer, he was, of all nonprofessional architects knows, the most _____ in that he was the least constrained by tradition or precedent.
Select the two answer choices that, when used to complete the sentence, fit the meaning of the sentence as a whole and produce completed sentences that are alike in meaning