Ron,

I’m having little trouble to get this thing. Every time I see this one option E first comes to mind because of the below mentioned problem.

1. When you say the above parallelism I guess the sentence structure should be

People killed by G.W.S are fewer than those killed by bee stings.

So here we must use 'that'. Without ‘that’ the sentence is wrong.
Except the above structure we can not use ‘that/those’.

In the below problem we need to use ‘that’ to refer the income. Is this because ‘income’ is not the subject of the main sentence?

X is Y’s poorest state, with an annual per capita income of $$$$, lower than in the most impoverished countries of the world.
b) lower than that of

Please explain how to deal with such comparison problems.

good call. i know the problem to which you're making an analogy here (it's the bihar problem from OG).

i guess "that of" has a little more leeway in the exact parallelism department.
i.e. you can put "that OF" or "those OF" in parallel to anything that suggests a possessive structure. or at least that's what we learn from this problem...

in any case, you can't use "IN any other...", because there's nothing to which the preposition IN can be parallel.

Ron I like all your explanation and for verbal they are the best out there. That is the reason I have left all other forum these days and visiting only mgmat, though since all other sources are ban here, only gmatpreps are of help :(

Coming back to this questions can we give this simple explanation here:

Only seven people this century have been killed by the great white shark, the man-eater of the movies—less than have been killed by bee stings.

The simple explanation I am referring here, is the mother of all confusion here is the noun people is missing in second part of comparison, the rule book of comparison says(which rule book? shy) all repeat noun/pronoun can be dropped in the second part of the comparison (ellipsis...) provided they are clear from the context, since people is obvious noun missing, that should be acceptable.

What do u say, also is it possible for you to summarize commonly ellisized gmat q

i'm sorry, i don't really understand what you're asking me here. could you please re-phrase your question? or use quotes, or indicate in some other way the boundary between your own question(s) and the material you're quoting?

Ron, WOULD it be correct to have a comma, rather than a dash in answer choice B? In other words, can you have back-to-back appositives set off by commas (given of course that the appositive was correct, as in B)?

yes, that would be fine. such punctuation would, however, cause the sentence to lose some of its emphasis, and would therefore weaken the overall thrust of the sentence. i.e., the dash is used in this case to emphasize the surprising nature of the statistic published afterward; if a comma were used instead, that emphasis on the surprising nature would be lost.

although this is not one of them, there are indeed some sentences in which the dashes are required for comprehension. here's an example:

the rate of the reaction is affected by three physical variables, pressure, concentration, and velocity.
--> UNCLEAR (we don't know if "pressure, concentration, and velocity" ARE the three physical variables, or if this is in fact a list of six factors)

the rate of the reaction is affected by three physical variables -- pressure, concentration, and velocity.
--> CLEAR (in this case, the only reasonable interpretation is that pressure, concentration, and velocity ARE the three physical variables)