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题库 / OG2018-SC-699
Researchers now regard interferon as not a single substance, but it is rather a biological family of complex molecules that play an important, though not entirely defined, role in the immune system.
as not a single substance, but it is rather a biological family of complex molecules that play
as not a single substance but as a biological family of complex molecules playing
not as a single substance but as a biological family of complex molecules that play
not to be a single substance but rather a biological family of complex molecules playing
not as a single substance but instead as being a biological family of complex molecules that play
that 这个从句修饰了molecules, so use "play" rather than "plays"
明白了
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