SC - how to decide about "either"

[Guest]

Genetic engineering sometimes entails plant or animal genes’ getting spliced into other species’ DNA, either to improve crop yields or for warding off insects or disease.

A. plant or animal genes’ getting spliced into other species’ DNA, either to improve crop yields or for warding off
B. plant or animal genes that get spliced into the DNA of other species, either for improving crop yields or the warding off of
C. the splicing of plant or animal genes into other species’ DNA, to either improve crop yields or to ward off
D. splicing plant or animal genes into the DNA of other species, either to improve crop yields or to ward off
E. splicing of plant or animal genes into the DNA of other species, for either the improvement of crop yields or to ward off

In the above example can some one please explain how to choose between c and d. I am guessing that answer should be from c and d.

how to decide about "either". whether "either" should come before "to" or after "to".

Can someone please explain the general logic behind this so that I can apply this to other sentences with same structure.

[Blue_Lotus]

The answer here is D

The idiom as you have spotted is either X or Y
Note that you have to maintain parallelism .

The infinitive form or any form that follows one of the element should be followed by the second form.
I mean X and Y should look same.
Example:
EITHER eating OR drinking ( correct, X (eating) and y(drinking )are parallel)
EITHER to eat OR to drink ( correct, X (to eat) and y(to drink) are parallel)
EITHER to eat OR drinking ( wrong not parallel)

In Answer choice C we have EITHER improve OR to ward ( X ( improve) is not parallel with Y(to ward) )
This is corrected in answer choice D.

When the TO is before either it is for the entire phrase (either ..OR..) so the correct
Way to use it would be " to either imrove or ward off ). No need for another TO before WARD.

In answer D where to is following EITHER, it is only for items insider the EITHER ...OR ,so we need to repeat it
For the part after OR...

[esledge]

Please cite the source (author) of this problem. We cannot reply until then. If no source is cited, we will have to delete the question just to be sure we are not violating someone else's copyright. Thanks!

Blue_Lotus is correct, but there is something else I'd like to mention once you post the author.

[pmal04]

I have seen it in GMATprep.
Hi Stacy,
My question: In choice D, is the word 'splicing' used as gerund?
Would 'the splicing' be more appropriate than 'splicing'?

[JonathanSchneider]

Yes, D is correct. Blue_Lotus is correct in regards to the parallelism.

There is also an "overly concise" form in C: "into other species' DNA" is not quite as good as "into the DNA of other species." This is discussed in our SC book under Concision forms. I wouldn't want to go on that alone, so I'm glad the parallelism issue is here as well, but it's worth pointing out.

Moreover, "entails" sort of equates "engineering" with "splicing." It makes sense to leave off the "the" for "splicing" to keep these two forms the same.

[violetwind]

Moreover, "entails" sort of equates "engineering" with "splicing." It makes sense to leave off the "the" for "splicing" to keep these two forms the same.

Hi insturctor,

I wanna confirm about the difference between the usage of "splicing" and that of "the splicing".

I don't quite understand how "entail" has anything to do with the choices.

if a simple gerund is the subject ,should a simple gerund /but not a complex gerund be the object? what's the point to keep this agreement or there's some meaning difference?

Thank you in advance.

P.S."simple/complex gerund" are the terms that I remembered I read from Manhattan's SC guide, hope my memories are right.
in this problem, simple gerund---splicing; complex gerund--the splicing.

[jnelson0612]

"entail" means "to cause or involve by necessity or as a consequence"; thus, I think Jonathan is saying that if A entails B then A and B should be the same part of speech.

For example:
Running a marathon entails training regularly.

Thus, you are correct that we should keep simple gerunds and we should in fact use them in for both A and B in this sentence.

Hope this clears things up!