Sentence Correction

Before we start breaking this sentence apart, let's look at the differences between the answer choices to see what kinds of errors we might be dealing with. We notice quite a few changes in tense ("providing" vs. "provided", "milking" vs. "milked", and "are producing" vs. "produces" "will produce"), but we should also notice something simple: the change from "cows" to "cow". Whenever we see changes between singular and plural in answer choices, we should immediately look for issues with pronoun agreement. We find our pronoun in the non-underlined portion of our sentence: "For the farmer who takes care to keep them cool".

Because this part of the sentence isn't underlined, we know that the sentence must discuss "Holstein cows", not "the Holstein cow". We can eliminate B and D.

Now we can look at the structure of the sentence. We see that the sentence begins with a list of three things the farmer does to cause the Holstein cow to produce more milk. A list is just a series of three or more items, which means we need to start thinking about parallelism. Since the first list item is not underlined, we want to match the structure of the second and third items to the first.

Looking at A, we see that the farmer

• takes care to keep them cool

• providing them with high-energy feed

• milking them regularly

So all of our list items involve verbs, but the -ing verbs in the second two list items don't match any tenses in the first list item. Eliminate A.

Note: some might think that "providing ... regularly" might act as a modifying phrase for "takes care to keep them cool", making an -ing verb a good pick (as in "I quickly called the office, holding my breath and hoping they wouldn't be closed"). However, it doesn't make much sense that feeding and milking cows would describe keeping them cool. Similarly, the comma between "feed" and "milking" would not be grammatical outside of a list.

C sets up a similarly confusing list. The farmer keeps the cows

• cool

• provided with high-energy feed

• milking them regularly

"Cool" and "provided" both act as adjectives to describe the cows, but now "milking" doesn't fit the structure. We can eliminate C, leaving us with E, in which the farmer keeps the cows

• cool

• provided with high-energy feed

• milked regularly

We actually featured this problem recently on the PrepScholar GMAT blog as one of the 5 Hardest Sentence Correction Questions. I recommend checking out the article for more strategies and trends we can take away from this and other 700+ level problems!