This tip for improving your GMAT score was provided by David Newland at Veritas Prep.
The words “do” and “does” sometimes function much like pronouns for verbs, as when they refer back to a previous word in the sentence and allow for a variation in grammar. With a pronoun, you can say, “My instructor enjoys critical reasoning, and she is good at it.” Not only is the word “she” an acceptable alternative to repeating “my instructor,” but the use of this word creates a much better sentence. “My instructor enjoys critical reasoning, and my instructor is good at it” sounds strange indeed. It sounds as if you are talking about two different people.
The word “do” in its various forms can function in the same way a pronoun does. It can be used in a sentence to stand in for another verb so long as the implied word is the same number (singular vs plural) and tense (past/present/future) as the word it stands in for.
For an example, look at the first sentence of the previous paragraph. I used the word “does” at the end of the sentence to stand for “functions.” The sentence means, “The word ‘do’ in its various forms can functions in the same way a pronoun functions.” Just as with the pronoun “she,” use of the word “does” is not only acceptable but also makes for a better sentence. Repeating the word “functions” is not as elegant a construction.
Using “Do” and “Does” Properly
Try this question from the Veritas Prep Question Bank.
Vinegar, an ingredient of many marinades, acts like a preservative, just like olive oil.
A) Vinegar, an ingredient of many marinades, acts like a preservative, just like olive oil.
B) Like olive oil, many marinades have vinegar as a preservative.
C) An ingredient of many marinades, vinegar acts like a preservative, as does olive oil.
D) Vinegar, an ingredient in many marinades, acts as a preservative, as does olive oil.
E) As olive oil, vinegar, an ingredient in many marinades, acts as a preservative.
The first answer choices to eliminate on this question are choices B and E. These choices are each very awkward. Choice B seems to imply that olive oil is like many marinades andhas vinegar in it. Choice E seems certainly to mean that vinegar is olive oil.
The remaining choices have a few decision points we can focus on. The first is the difference between “like” and “as.” Choice A has the word “like” repeated. If we ignore the modifier “an ingredient of many marinades,” choice A reads, “Vinegar … acts like a preservative, just like olive oil.” The second use of “like” in this case is not correct. Look at choice C for a comparison. If vinegar is acting like a preservative and olive oil is acting like a preservative, you would need to use “as” instead of “like.”
“As” is the proper wording for a comparison of action. “I walk every day, as do you” means that we each go for a walk each day. The sentence, “I walk every day like you” means that I am imitating you as I walk. If we are both doing the same thing or performing the same action, we use “as.” Choice A is eliminated.
Choices C and D each properly use the present tense singular “does” to stand for “acts as.” Choice D says, “Vinegar, an ingredient in many marinades, acts as a preservative, as does olive oil.” It is clear that “does” means “acts as.” Vinegar acts as a preservative and olive oil acts as a preservative.
The only important difference between these answer choices is that choice C uses “like” in place of the first “as.” “Vinegar … acts like a preservative, as does olive oil.” The problem with choice C is not the word “does,” which is properly used, but the fact that C seems to imply that vinegar has something in common with a preservative; that it is “like a preservative.” When it is clear from the context that the vinegar acts as a preservative (and so does olive oil).
Do not be afraid of “do” and “does” in sentence correction. So long as the word is referring back to a verb that is the same number and tense, it is not only acceptable; it can also make for a better sentence. In fact, it usually does.
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