Sentence Correction (SC) | Re: Researchers now regard interferon as not a single

Researchers now regard interferon as not a singlesubstance , but it is rather a biological family of complex molecules that play an important, though not entirely defined, role in the immune system.
Elimination Sequence: A, D, E
A. as not a single substance, but it israther a biological family of complex molecules that play -[color=#004b80] As not a substance but it israther a family, is what should be the structure. Not X but Y. Additionally using another contrast word e.g. RATHER when BUT is
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