Some of the most difficult SAT writing questions deal with correct comparisons between nouns. Parallelism in general is an SAT grammar favorite, but this specific type of parallelism issue is notoriously hard to spot.
Why comparison problems go unnoticed
There are two major reasons why they cause such a problem. The first is that we make these kinds of “mistakes” pretty often in conversation. To the untrained proofreader, they seem pretty natural.
The second is that they can often be fixed with a possessive. If you want to compare the color of Sam’s and Brian’s tongues, then the sentence “Sam’s tongue is redder than Brian” is clearly weird, whereas “Sam’s tongue is redder than Brian’s” would be just fine. That’s all well and good, but the SAT might not make it so easy for you. Instead, the two nouns may already be plural.
✗ Oranges’ skins are tougher than lemons.
✓ Oranges’ skins are tougher than lemons’.
And that’s a little tricky because the only difference is the apostrophe.
The key word for comparison problems
Let’s take a look a fairly convoluted identifying sentence error question.
Now this is a lot more SAT-like. If you were to see this on your test, you’d be wise to note the word “than.” It almost always signals that we’re making a comparison, so you know to check for a problem there.
After noticing the “than,” we should look for the adjective or verb that it’s being paired with, e.g. “enjoy more than” or “is easier than.” In the sentence above, our adjective is “greater.”
Finally, find the nouns—where the problem might happen. In the sentence above, the two that are being compared are “impact” and “shorts,” and that’s not okay. We should be comparing two similar objects, like two shorts or two impacts. So we have to change one of the two, but which one?
That has to do with the comparison being made. What’s “great” (meaning large, not good) in this sentence? Although the “impact” is, the “upcoming shorts” aren’t, so that’s the side we’ll change. There are a couple of ways to modify it. The first is to change it to “than that of the upcoming shorts,” so “that” refers to “impact.” The second is to add in that possessive. Shorts becomes shorts’.
Remember that the SAT writing multiple choice is a constant process of elimination. If you see a pronoun underlined, check its antecedent. When you see a comparison in the sentence, look for the nouns on either side of “than.”