Hydrocarbons, with which fruit flies perfume themselves in species-specific blends, are known to be important in courtship, and apparently this assists flies that taste the hydrocarbons on prospective mates to distinguish their own species from that of others.
A. and apparently this assists flies that taste the hydrocarbons on prospective mates to distinguish their own species from that of
B. and apparently this assists flies when they taste the hydrocarbons on prospective mates in distinguishing their own species from those of
C. which apparently assists flies that tastes the hydrocarbons on prospective mates in being able to distinguish their own species from
D. apparently assisting flies to taste the hydrocarbons on prospective mates to distinguish their own species from those of
E. apparently assisting flies that taste the hydrocarbons on prospective mates in distinguishing their own species from

A is wrong because "this " is ambiguous and also "from that of "
B is wrong "when"
C being
betwen D and E why D is wrong because if we say "their own species from those of others" so those refers to species or technically to whole "their own species " or there are other errors in D.
Please explain
This is GMAT Prep Question

choice d: you're right that 'those of others' is problematic; it should just be 'others' (it's clear that the intention is to refer to other species, not to something of other species).

another huge problem with choice d is its total distortion of the sentence's original meaning.
- the original meaning is that hydrocarbons assist those flies that happen to taste them in species identification.
- choice d asserts that hydrocarbons somehow help flies to taste hydrocarbons (other ones?) with the intention** of species identification, which is a whole different ballgame.

**the infinitive can signal intention, or purpose, in this sort of context. for instance,
i ran over the glass in the road, flattening my tire --> the flattening of the tire was a result, but no information is given as to whether i intended it (i probably didn't)
i ran over the glass in the road to flatten my tire --> for some reason, i actually wanted to flatten the tire, so i chose this particular method of doing so.

Thanks for the nice explanation. Can you also please tell whether "assist in" is correct or "assist to" is the correct idiom - if at all there is a rule?

Thanks

good question.

from what i've seen, 'assist ... in' is the generally preferred form. i'm not so confident as to say that 'assist X to do y' is just plain wrong, but 'in' is preferred.

in any case, check out the official explanations (the ones appearing in the o.g.). if they tell you that 'assist ... to' is unidiomatic / awkward / whatever, then take that as gospel in the future.

D. apparently assisting flies to taste the hydrocarbons on prospective mates to distinguish their own species from those of
E. apparently assisting flies that taste the hydrocarbons on prospective mates in distinguishing their own species from

the modifier is placed so far away from the Subject ???

and of course... it is not modifying are know to be important ??


Ron Please help

Ron could you please also explain what others is referring to ??

OWN species or just species ??
own would act as a qualifier here..right ?

check out the parallelism:
...in distinguishing their own species from others

according to that parallel structure, "others" must refer to other species, since that's the only way in which logical parallelism can be achieved.

which modifier? you mean the "assisting ... in" modifier?
that's an adverbial modifier: "-ing" followed by a comma. it modifies the action or main verb of the most proximate clause: in this case, "are known to be important in courtship".