Pronoun Ambiguity

[vishalc581]

Can you please explain why below sentence is right. I mean how THEY is referring to supernovas and not chemicals, environments and elements.

Supernovas destroy their immediate environments in vast explosions, but by synthesizing
heavy chemical elements, THEY provide the universe with the possibility
of biochemistry-based life as we know it.



What if comma is changed to semi-colon:

Supernovas destroy their immediate environments in vast explosions, but by synthesizing
heavy chemical elements; THEY provide the universe with the possibility
of biochemistry-based life as we know it.

Is it correct now?


I am facing difficulty in understanding pronoun ambiguity especially like the above. Can you please explain the same in more details with examples.

[Chelsey Cooley]

First, let's look at your semicolon example:

Supernovas destroy their immediate environments in vast explosions, but by synthesizing heavy chemical elements; THEY provide the universe with the possibility of biochemistry-based life as we know it.

The only rule of semicolons is that you need a complete sentence on either side of the semicolon. The second bit is a complete sentence, since it has a subject and verb:

THEY provide the universe with the possibility of biochemistry-based life as we know it.

But unfortunately, the first bit isn't a complete sentence, because it uses 'but' incorrectly. To create a complete sentence with the conjunction 'but', you need to join two things that match. In this case, we're joining a sentence with a modifier. That's not allowed:

Supernovas destroy their immediate environments in vast explosions, but by synthesizing heavy chemical elements

So, our first conclusion is that the semicolon version is wrong.

Now for your other question. The answer is that on the GMAT, it doesn't matter. There are many sentences where a pronoun can technically refer to multiple different nouns in the sentence. Those sentences are still grammatically correct, as long as there's something in there that the pronoun can correctly refer to. When you see a pronoun that could have two different referents on the GMAT, here's what to ask yourself:

1. Are there any other answer choices that remove the 'ambiguity' and are completely correct otherwise? If so, pick that answer choice instead of the one with the ambiguity.

2. If not, then can you identify a grammar problem with every other answer, and no other grammar problem (except 'ambiguity') with your answer? Then pick your answer.

That is, ambiguity can make one answer better than another, but it doesn't necessarily make an answer wrong when you see it by itself.

[vishalc581]

I understood the ambiguity point.

But I have a doubt in sentence when I replaced with semi-colon.

What is "BUT" acting as in that first part of the sentence before the semi-colon. Is it acting as a preposition.

I know I don't need to know various grammar terms for GMAT but that is how I distinguish various concepts in my mind.

[tim]

No, "but" is NEVER a preposition. Be sure to get some practice identifying prepositions because that is vital to understanding the structure of sentences.

[vishalc581]

Hi Tim,


I have read in MGMAT GMAT verbal foundations book that BUT can also be preposition.

Please see below sentence from the book:

"All developed nations but the U.S. have some form of national health insurance."

am I missing something or understanding it wrong. Please help.

[tim]

I don't think I've ever seen something like this on official GMAT questions, but it sounds like the example you brought up is confusing you more than it is helping. So unless and until you learn how to tell the difference, my advice is to just assume "but" will never be used as a preposition.