GMATGuruNY wrote:

Crystal W wrote:Recently physicians have determined that stomach ulcers are not caused by stress, alcohol, or rich foods, but a bacterium that dwells in the mucous lining of the stomach.

　　(A) not caused by stress, alcohol, or rich foods, but

　　(B) not caused by stress, alcohol, or rich foods, but are by

　　(C) caused not by stress, alcohol, or rich foods, but by

　　(D) caused not by stress, alcohol, and rich foods, but

　　(E) caused not by stress, alcohol, and rich foods, but are by
My question is about and/or. The OG said "and identifies the combination of these three factors as a suggested cause of stomach ulcers, whereas or offers three individuals possibilities." Can someone explain this function? I think and should be replaced of or in negative sentence.
Thanks in advance!

In the idiom not X but Y, X and Y must be PARALLEL FORMS.

A: not caused...but a bacterium
Here, caused (participle) and a bacterium (noun) are not parallel forms.
Eliminate A.

B: not caused...but are
Here, caused (participle) and are (verb) are not parallel forms.
Eliminate B.

D: not by...but a bacterium
Here, by (preposition) and a bacterium (noun) are not parallel forms.
Eliminate D.

E: not by...but are
Here, by (preposition) and are (verb) are not parallel forms.
Eliminate E.

The correct answer is C.

D and E: Ulcers are caused not by stress, alcohol and rich foods.
Here, the usage of and implies the following:
Stress, alcohol and rich foods do not work together AS A GROUP to cause ulcers.
However:
It is possible that stress ON ITS OWN causes ulcers.
It is possible that alcohol ON ITS OWN causes ulcers.
It is possible that rich foods ON THEIR OWN cause ulcers.
Not the intended intended meaning.
Eliminate D and E.

The intended meaning is conveyed by the OA:
Ulcers are caused not by stress, alcohol or rich foods.
Here, the usage of or implies the following:
Stress does not cause ulcers.
Alcohol does not cause ulcers.
Rich foods do not cause ulcers.

Thank you but I am still a little confused. Do you mean "or" means combination in the negative sentence? Also, According to the common sence, I believe the cause should be one of three not the combination.

Crystal W wrote: Thank you but I am still a little confused. Do you mean "or" means combination in the negative sentence? Also, According to the common sence, I believe the cause should be one of three not the combination.

To convey not x and not y, we say the following:
not x OR y.
The following is INCORRECT:
not x AND y.

The SC above intends to convey the following meaning:
Ulcers are not caused by stress, ulcers are not caused by alcohol, AND ulcers are not caused by rich foods.
To convey this meaning, we say the following:
Ulcers are not caused by stress, alcohol OR rich foods.
The following is INCORRECT:
Ulcers are not caused by stress, alcohol AND rich foods.
Eliminate D and E.

Hello Everyone!

This is a great example of a sentence that focuses on parallelism, so let's dive in! To start, let's take a quick look at the original question, and highlight the main differences in orange:

Recently physicians have determined that stomach ulcers are not caused by stress, alcohol, or rich foods, but a bacterium that dwells in the mucous lining of the stomach.

A. not caused by stress, alcohol, or rich foods, but
B. not caused by stress, alcohol, or rich foods, but are by
C. caused not by stress, alcohol, or rich foods, but by
D. caused not by stress, alcohol, and rich foods, but
E. caused not by stress, alcohol, and rich foods, but are by

After a quick glance over the options, there are a few things we can focus on:

1. not caused / caused not (parallelism/idioms)
2. or / and (meaning/lists)
3. but / but are by / but by (parallelism/idioms)

Since we know this question mainly focuses on parallelism, let's tackle #1 & #3 on our list at the same time. This is the idiom structure we're working with here:

not X, but Y

Both X and Y must be written using parallel structure, including word placement, verb tenses, singular/plural, etc. Since the phrase "caused by" is included in this sentence, we need to be careful to make sure it's included in both X and Y only if it appears after the word "not:"

not caused by X, but caused by Y = PARALLEL
not caused by X, but Y = NOT PARALLEL

caused not by X, but by Y = PARALLEL
caused not by X, but caused by Y = NOT PARALLEL
caused not by X, but Y = NOT PARALLEL

Let's add in the end of the sentence to see which options use parallel structure, and eliminate those that don't:

A. not caused by stress, alcohol, or rich foods, but a bacterium that dwells in the mucous lining of the stomach. --> not caused by X, but Y = NOT PARALLEL

B. not caused by stress, alcohol, or rich foods, but are by a bacterium that dwells in the mucous lining of the stomach. --> not caused by X, but are by Y = NOT PARALLEL

C. caused not by stress, alcohol, or rich foods, but by a bacterium that dwells in the mucous lining of the stomach. --> caused not by X, but by Y = PARALLEL

D. caused not by stress, alcohol, and rich foods, but a bacterium that dwells in the mucous lining of the stomach. --> caused not by X, but Y = NOT PARALLEL

E. caused not by stress, alcohol, and rich foods, but are by a bacterium that dwells in the mucous lining of the stomach. --> caused not by X, but are by Y = NOT PARALLEL

There you have it! Option C is correct because it's the only one that uses parallel structure within the idiom "not X, but Y." By focusing on parallelism, you should be able to answer this question pretty quickly!


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