GMAT Sentence Correction: How to Find the Core Sentence - Part 2
Welcome to the second installment of our Core Sentence series; if you havent yet read Part 1, do so now before continuing with this segment. How has your practice been going? Its hard to develop the ability to grey out parts of the sentence in your mind. Did you find that you were able to do so without writing anything down? Or did you find that the technique solidified better when you did write out the core sentence?
Most people do have to start, in practice, by writing out the core. The goal is to be able to do everything (or almost everything) in your head by the time the real test rolls around.
Try out this GMATPrep problem from the free exams; give yourself about 1 minute 20 seconds. (You can always choose to spend a little longer, since that time is an average, not a limit; more than about 20-30 seconds longer, though, typically just indicates that youve gotten stuck. At that point, guess from among the remaining answers and move on.)
* Galileo did not invent the telescope, but on hearing, in 1609, that such an optical instrument had been made, he quickly built his own device from an organ pipe and spectacle lenses.(A) Galileo did not invent the telescope, but on hearing, in 1609, that such an optical instrument had been made, he
(B) Galileo had not invented the telescope, but when he heard, in 1609, of such an optical instrument having been made,
(C) Galileo, even though he had not invented the telescope, on hearing, in 1609, that such an optical instrument had been made, he
(D) Even though Galileo did not invent the telescope, on hearing, in 1609, that such an optical instrument had been made,
(E) Even though Galileo did not invent the telescope, but when he heard, in 1609, of such an optical instrument being made, he
The First Glance shows a possible sentence structure issue: The first two start with a noun and verb, while the third tosses in a comma after that subject. Im definitely going to need to check for that verb later!
The final two start with even though, which signals a clause, but a dependent one. That means Ill have to make sure theres an independent clause (complete sentence) somewhere later on.
Time to read the original sentence. Its decently complex. Whats the core sentence?
Heres the core:
Galileo did not invent the telescope, but he built his own device.
This actually consists of two complete sentences connected by a comma and conjunction. Theres nothing wrong with the core on this one. Now, you have a choice. You can check the modifiers in the original sentence (and, indeed, if you did spot any problems, youd want to go deal with those right away). If not, though, then start with those potential structure issues spotted during the first glance.
Strip out the core for the other four answers:
(B) Galileo had not invented the telescope, but quickly built his own device.(C) Galileo he quickly built his own device.
(D) Even though Galileo did not invent the telescope, quickly built his own device.
(E) Even though Galileo did not invent the telescope, but he quickly built his own device.
Excellent! Now we have something to work with! Answer (C) doubles the subject; we dont need to say both Galileo and he.
Answers (D) and (E) both start with even though, creating a dependent clause. Answer (D) doesnt have an independent clause later because the part after the comma is missing the subject he.
Note: answer (B) might appear to have the same problem as (D), but the structures are not the same. Answer (B) begins with an independent clause. In this case, its okay to say the subject only once at the beginning and then attach two different verbs (had not invented and built) to that subject. (You may still think this one sounds funny. More on this below.)
Answer (E) does have an independent clause later, but theres a meaning problem. The word but already indicates a contrast. Using both even though and but to connect the two parts of the sentence is redundant.
Okay, (C), (D) and (E) have all been eliminated. Now, compare (A) and (B) directly.
(A) Galileo did not invent the telescope, but on hearing, in 1609, that such an optical instrument had been made, he(B) Galileo had not invented the telescope, but when he heard, in 1609, of such an optical instrument having been made,
There are a couple of different ways to tackle this, but Im going to stick to the sentence structure route, since thats our theme today. Answer (B) does have one more clause in it, though its a dependent clause:
Galileo had not invented the telescope, but when he heard of such an optical instrument having been made, quickly built his own device.
Now, we do have a problem with the structure! If that intervening dependent clause werent there at all, then the core could have been okay: Subject verb, but verb. Technically, you wouldnt want a comma there, but thats really the only small issue.
When, however, you introduce a dependent clause in the middle, you cant carry that original subject, Galileo, all the way over to the second verb at the end. Instead, as with answer (D), you need a complete sentence after the when dependent clause, something like:
Galileo did not invent the telescope, but when he heard that one had been made, HE quickly built his own device.
Answer (B) is also incorrect.
The correct answer is (A).
You're halfway through! Join me next time, when we'll take a look at another type of complex sentence structure used commonly on the GMAT.
Key Takeaways: Strip the sentence to the Core, part 2
(1) In the Galileo problem, only the correct answer contains a legal core sentence. Though there are other ways to eliminate answers on this problem, you still need to learn how to deal with structure. GMAC (the organization that makes the GMAT) has said for several years now that they are including more SC problems in which you really do have to understand the underlying meaning or sentence structure in order to get yourself all the way down to the right answer.
(2) Complex sentence structures can come in many flavors. One of the most common is the compound sentence, which consists of at least two complete sentences connected by a comma + conjunction or a semi-colon. The comma conjunction structure will use the FANBOYS (For And Nor But Or Yes So). You can learn more about the FANBOYS in chapter 3 (Sentence Structure) of our 6th edition Sentence Correction Strategy Guide.
(3) A sentence can also contain dependent clauses (and the complicated sentences we see on the GMAT often do). Common words that signal a dependent clause include although, if, since, that, unless, when, and while. You can learn more about these in chapter 4 (Modifiers) of our 6ED SC guide.
* GMATPrep questions courtesy of the Graduate Management Admissions Council. Usage of this question does not imply endorsement by GMAC.