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.
(This question is from Official Guide. Therefore, because of copyrights, the complete question cannot be copied here. The question can be accessed at GMAT Club)
- Researchers now regard interferon as (Main Subject: Researchers; Main Verb: regard)
- not a single substance, (First element of the list)
- but it is rather a biological family of complex molecules (Second element of the list)
- that play an important, though not entirely defined, role in the immune system. (Dependent clause modifying ‘molecules’ – Subject: that; Verb: play)
The sentence talks about what researchers regard interferon as and what researchers do not regard interferon as. The researchers do not regard interferon as a single substance; they regard interferon as a biological family of complex molecules. These molecules play an important but not entirely defined role in the immune system.
The sentence has two issues:
- Deterministic parallelism error: By replacing the list with individual elements, we get the following two structures:
- Researchers now regard interferon as a single substance (Makes sense)
- Researchers now regard interferon as it is rather a biological family of complex molecules (Doesn’t make sense)
Since the second structure doesn’t make sense, the list is incorrect.
- Even though the construction ‘regard X as not Y but Z” is parallel, it is generally not used. The better construction is ‘regard X not as Y but as Z’.
(A) Incorrect. For the reasons mentioned above.
(B) Incorrect. This option also has a parallelism error. When we replace the list with the second element, we’ll get two ‘as’. The structure will be ‘as as a biological family’.
(D) Incorrect. For the following reasons:
- ‘Regard…to be’ is only used in the form ‘X is regarded to be Y’, not ‘A regards X to be Y’. Therefore, in this sentence, ‘regard…to be’ is incorrect.
- Even if we replace ‘to be’ with ‘as’, the sentence will incorrect since there is no ‘as’ after ‘but’.
(E) Incorrect. The use of ‘being’ distorts the meaning since it seems to indicate a temporary state – as if interferon is regarded as being a biological family for a temporary time frame. The use of ‘instead’ is also redundant.
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