Scientists believe that unlike the males of most species

[inc.manni]

Would C have been correct if:

by using acoustical signals, not BY using olfactory ones, and by attracting

Reason: X (by using acoustical signals) NOT Y (BY using olfactory ones), and Z (by attracting) -- X, NOT Y, and Z - Parallel

Would E have been correct if:

using acoustical signals, not USING olfactory ones, and attracting

Reason: X (using acoustical signals) NOT Y (USING olfactory ones), and Z (attracting) -- X, NOT Y, and Z - Parallel

Regards

[inc.manni]

I think even if we use parallel structures as below, meaning conveyed is not correct.

1. using acoustical signals, not BY using olfactory ones, and by attracting

2. using acoustical signals, not USING olfactory ones, and attracting

It changes the meaning:

whistling moths of Numbing, Australia, call female moths to them, using acoustical signals, not BY using olfactory ones, and by attracting

Now these whistling moths don't call females by attracting them during the day, rather than at night.

Calling is not related in any way to attracting - but using signals of one type rather than of other - is surely connected.

Its better to say moths calls their females, using signals of one type rather than of other, and attract their mates during the day, rather than at night.

Would welcome experts comments.

Regards

[RonPurewal]

Would C have been correct if:

by using acoustical signals, not BY using olfactory ones, and by attracting

Reason: X (by using acoustical signals) NOT Y (BY using olfactory ones), and Z (by attracting) -- X, NOT Y, and Z - Parallel

Would E have been correct if:

using acoustical signals, not USING olfactory ones, and attracting

Reason: X (using acoustical signals) NOT Y (USING olfactory ones), and Z (attracting) -- X, NOT Y, and Z - Parallel

Regards

nope. nonsense meaning.
the implication here is that there are THREE ways to CALL FEMALES:
• using acoustical signals,
• NOT using olfactory signals,
• attracting them at time xxxxx.

only one of these is a way to call females (the first one).

[RonPurewal]

it's possible for 'not doing x' to make sense in some parallel context.
e.g.,
You can ace the GMAT by managing your time well and not rushing through the text of the problems.

you can see the difference:
'managing your time well' is a way to ace the test.
'NOT rushing' is ANOTHER way to ace the test.

this doesn't work here, since 'not using olfactory signals' isn't A WAY TO CALL FEMALES.

[RonPurewal]

MOST IMPORTANTLY

DO NOT 'make your own versions' of GMAC's sentences.
really.
don't do it.

the GMAT only tests 1-2% of the things that can actually go wrong with english sentences (and even that may be an overestimate).
when random users try to 'edit' these sentences, the result is almost always incorrect—for reasons that the GMAT doesn't test.

making your own examples is good, but they should be...
...1/ your own examples,
...2/ SIMPLE examples, each illustrating only ONE concept (that is actually tested on this exam).

as far as the official problems are concerned, the given answer choices should offer more than enough challenges already.
(:

[aflaamM589]

even i have same doubt as vijaya.

Rather than is usually used to show preference of verbs (or clauses) .but here it is used to show preference b/w 2 nouns. Is it correct usage?

"instead of" is generally restricted to nouns.

"rather than" can be used for essentially any part of speech at all.

they moved stiffly rather than gracefully (adverbs)
they moved to the left rather than to the right (prepositional phrases)
the car was red rather than blue (adjectives)
i bought a car rather than a truck (nouns) <–– this is the only sentence here that would work with 'instead of'
he chose to leave rather than continue arguing (infinitives)

...etc

there is also a difference in meaning, but that difference is much too slight to be relevant to this exam.

Dear Ron,
Can instead of also be used with gerunds?
For instance
I chose to skiing instead of exercising
Thanks

[RonPurewal]

i don't know what a "gerund" is.

I chose to skiing instead of exercising

this ^^ doesn't help me figure out what you are asking, either, since it's not a sentence in the first place. (you can "choose to ___", but you can't "choose to ____ing".)

[NicoleT643]

Hi Ron, another reason I eliminated A is the repetition of "they" after "and". Obviously it is not one of the hard rule issues and I remember that some correct answers repeat the subject after and/or.
Would you please advice whether I was correct ? And in what circumstance should the subject repeat and in what circumstance it should not? Is this a very minor issue that we don't have to consider when we solve the problem? Thank you.

[RonPurewal]

Hi Ron, another reason I eliminated A is the repetition of "they" after "and". Obviously it is not one of the hard rule issues and I remember that some correct answers repeat the subject after and/or.
Would you please advice whether I was correct ? And in what circumstance should the subject repeat and in what circumstance it should not? Is this a very minor issue that we don't have to consider when we solve the problem? Thank you.

^^ if this is the ONLY difference between two choices, then consider it. otherwise, don't.

[YuanqiZ223]

Hi Ron,

Could you please explain why A is wrong?

Since when I did this question for the first time, I can't tell if the two types of signals are together or not. (In your example, 'I saw A but not A's wife' is okay to use 'but not' if we usually see A and A's wife together. However, in the real test, I can't really tell if that is the case here, as I am not familiar with these two types of signals.

Therefore, should I eliminate that kind of use of 'but not' unless I am sure they are together?

Thank you!

[Sage Pearce-Higgins]

The split between 'but not', 'not', 'instead of', and 'rather than' is a really tricky one. When I first did this problem I had to think hard about the meaning. Since they use one type of signal in place of another, 'instead of' or 'rather than' is correct. You can probably hear that this sentence is wrong:
I went to the store by bicycle but not by car.
But GMAT isn't that mean. There's another much easier split, and it's a classic one. The word 'and' needs to jump out as a parallelism marker, and the use of the pronoun 'they' is a typical error. When we have one subject doing two actions, we don't need to use a pronoun. For example, 'Ivan plays football and he watches movies.' is incorrect. Admittedly, this split is a bit obscured by the rest of the sentence, but that's what you need to train yourself to see.