Doctors generally agree that such factors as cigarette smoking, eating rich foods high in fats, and alcohol consumption not only do damage by themselves but also aggravate genetic predispositions toward certain diseases.
(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)
Doctors agree that certain factors do two things:
- damage by themselves
- worsen (aggravate) genetic inclination toward certain diseases
What are these factors? Factors similar to:
- cigarette smoking
- eating rich foods high in fats
- alcohol consumption
Now, if you know something about simple and complex gerunds and action nouns and you have read MGMAT book, you might know that the book states clearly that simple gerunds should never be mixed with complex gerunds or action nouns. However, in this sentence ‘cigarette smoking’ is a complex gerund, ‘eating rich foods’ a simple gerund, and ‘alcohol consumption’ an action noun, and all of these three are parallel (as they are in a list). So, what we can learn from this sentence is that it is not a strict rule that a simple gerund can never be parallel to a complex gerund or an action noun. However, I do think that if given two options with everything else same and one in which a simple gerund is parallel to a complex gerund and one in which both the elements are of the same kind, we should choose the latter one. The more parallel the structure is, the better it is.
The sentence does not have any error. The list in the underlined part is parallel. “do damage” and “aggravate” are both verbs and thus parallel to each other.
(B) Incorrect. For the following reasons:
- While ‘aggravate’ means worsen, a meaning that makes sense within the context of the sentence, ‘aggravating’ means ‘irritating’, a meaning that does not make sense within the context of the sentence. Thus, we cannot use ‘aggravating’.
- The use of ‘but also’ without ‘not only’ is not correct.
- Also, there appears to be no need to switch from simple present from first part of the list to present continuous in the second part of the list.
(C) Incorrect. For the following reasons:
- Error no. 1 of option B
- Error no. 2 of option B
- To present general facts, simple present is strongly preferred over present continuous.
(D) Incorrect. For the following reasons:
- Error no. 1 of option B
- Lack of parallelism: ‘not only’ does not have a corresponding ‘but also’. Please remember that such exception (‘not only’ without ‘but also’) is only allowed when both the structures are followed by independent clauses. Please refer to this question for more details.
- Error no. 3 of option B
(E) Incorrect. For the following reasons:
- Error no. 1 of option B.
- In this option “they are also aggravating” is another independent clause. Therefore, it is not clear whether this is also what doctors agree on or this is an additional information separate from the first independent clause.
- Error no. 3 of option C.