GRE Sentence Completion

Because they had various meanings in nineteenth-century biological thought,"mechanism"and "vitalism"ought not to be considered___terms ;thus,I find the recent insistence that the terms had single definitions to be entirely___.
(A) univocal..erroneous
(B) problematic..anachronistic
(C) intractable..obtuse
(D) congruent..suspect
(E) multifaceted..vapid

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Ans : (A) univocal..erroneous