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Hydrogen peroxide

by kaulnikhil » Thu Mar 04, 2010 12:35 pm
Hydrogen peroxide is more efficient at disinfecting bacteria than is heavy water, by its foaming action caused by the release of nascent oxygen.

A. Hydrogen peroxide is more efficient at disinfecting bacteria than is heavy water
B. Hydrogen peroxide is most efficient at disinfecting bacteria than is heavy water
C. Hydrogen peroxide is more efficient than heavy water at disinfecting bacteria
D. Hydrogen peroxide, more efficient than heavy water at disinfecting bacteria
E. Hydrogen peroxide disinfects bacteria more efficiently than heavy water

[spoiler]what is the problem with A? [/spoiler]
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by Osirus@VeritasPrep » Thu Mar 04, 2010 12:40 pm
You need a helping verb after "heavy water". You can't omit a helping verb otherwise there is ambiguity.

B is wrong because of "most". When comparing two things you use more

In terms of the other answers, I'm really not sure. This question seems wrong because the "its" in the non-underlined part of the sentence has more than one possible antecedent. What is the source?
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by reply2spg » Thu Mar 04, 2010 12:41 pm
C is correct here. A is not ||el.

Hydrogen peroxide is more efficient at disinfecting bacteria than is heavy water - 'Is' is for what? Why do we need 'is' here is not clear...therefore, A is not correct
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by kaulnikhil » Thu Mar 04, 2010 12:43 pm
reply2spg wrote:C is correct here. A is not ||el.

Hydrogen peroxide is more efficient at disinfecting bacteria than is heavy water - 'Is' is for what? Why do we need 'is' here is not clear...therefore, A is not correct
cant we put it as:
Hydrogen peroxide is more efficient at disinfecting bacteria than is heavy water at disinfecting bacteria
In that case wouldn't A be fine?

doesn't this make sense?
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by Osirus@VeritasPrep » Thu Mar 04, 2010 12:44 pm
kaulnikhil wrote:
reply2spg wrote:C is correct here. A is not ||el.

Hydrogen peroxide is more efficient at disinfecting bacteria than is heavy water - 'Is' is for what? Why do we need 'is' here is not clear...therefore, A is not correct
cant we put it as:
Hydrogen peroxide is more efficient at disinfecting bacteria than is heavy water at disinfecting bacteria
doesn't this make sense?
yes, that would be grammatically correct, but A omits the part after heavy water. That is why its wrong.

What is the source of this?
https://www.beatthegmat.com/the-retake-o ... 51414.html

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by kaulnikhil » Thu Mar 04, 2010 12:45 pm
osirus0830 wrote:
kaulnikhil wrote:
reply2spg wrote:C is correct here. A is not ||el.

Hydrogen peroxide is more efficient at disinfecting bacteria than is heavy water - 'Is' is for what? Why do we need 'is' here is not clear...therefore, A is not correct
cant we put it as:
Hydrogen peroxide is more efficient at disinfecting bacteria than is heavy water at disinfecting bacteria
doesn't this make sense?
yes, that would be grammatically correct, but A omits the part after heavy water. That is why its wrong.

What is the source of this?
Doesn't A omit the part because there is no need to repeat the same part .. something known as Ellipsis
Last edited by kaulnikhil on Mon Mar 08, 2010 1:15 pm, edited 1 time in total.
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by Osirus@VeritasPrep » Thu Mar 04, 2010 12:51 pm
yeah, you're right. A is still less preferable because it inverts the order with the subject and verb. It words it than is heavy water. In that clause heavy water is the subject and "is" is the verb. If given a choice you want to choose the answer that has the subject first and the verb after the subject.
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by gmatmachoman » Thu Mar 04, 2010 1:33 pm
osirus0830 wrote:yeah, you're right. A is still less preferable because it inverts the order with the subject and verb. It words it than is heavy water. In that clause heavy water is the subject and "is" is the verb. If given a choice you want to choose the answer that has the subject first and the verb after the subject.

I doubt the query...

what does the "its" refer to?

Ambiguous pronoun reference in the non-underlined portion...
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by lunarpower » Sat Mar 06, 2010 5:26 pm
i have serious doubts that this was ever an official problem -- the writing is absolutely atrocious. here are the two most flagrant errors:
* that word "disinfect" is not used correctly. you don't "disinfect" bacteria themselves; you disinfect surfaces or implements in order to get rid of bacteria. (the way this problem is literally written -- "disinfecting bacteria" -- it implies that you actually clean the bacteria themselves!)
* from a factual standpoint, this sentence is totally out to lunch. the term "heavy water" is used to refer to water with the hydrogen replaced by deuterium (a less common isotope of hydrogen). this substance is used for various purposes: for instance, as a neutron moderator in nuclear reactors, and also as an isotope marker in metabolic studies. it costs approximately $1000 per kilogram, and would never be used for so mundane a purpose as disinfecting things.

--

more problems:

* the referent of the pronoun "it" isn't totally clear. this is not a universal cause for elimination, of course -- there are plenty of correct official problems with somewhat ambiguous pronouns -- but in this problem it's not even 100% clear which of the two chemicals has the cited foaming action.

* the modifier "by its foaming action..." isn't used correctly. not only is it awkward, but it would also erroneously modify the principal verb in the main clause ("is more efficient").

--

the original poster claims that this problem is from "gmat sets". it seems that those sets, like the 1000sc problems, are a mishmash of (a) genuinely official problems, mostly from gmat prep, and (b) non-official problems that are, in the main, absolutely horrible and not worth studying at all.
this appears to be one of the latter.

still, we can have at least some productive discussion about this problem. see the post below.
Ron has been teaching various standardized tests for 20 years.

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by lunarpower » Sat Mar 06, 2010 5:27 pm
--

in any case:
of the five choices that are presented here, (a) is the best.
it's the only one that is completely parallel and unambiguous in terms of meaning. in fact, the extra "is" at the end of this sentence is absolutely necessary.
that helping verb is lacking in choice (e), thereby creating a non-acceptable ambiguity: that choice could potentially mean either "disinfecting bacteria" or "disinfecting heavy water". (both of these meanings are rubbish anyway -- see the discussion of meaning, above -- but it's the takeaway that matters.)

for another example of an official problem in which exactly the same structure as (a) is used, check out #106 in the og verbal supplement (the sentence about inuits and aleuts).
Ron has been teaching various standardized tests for 20 years.

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by kaulnikhil » Sun Mar 07, 2010 12:11 am
lunarpower wrote:--

in any case:
of the five choices that are presented here, (a) is the best.
it's the only one that is completely parallel and unambiguous in terms of meaning. in fact, the extra "is" at the end of this sentence is absolutely necessary.
that helping verb is lacking in choice (e), thereby creating a non-acceptable ambiguity: that choice could potentially mean either "disinfecting bacteria" or "disinfecting heavy water". (both of these meanings are rubbish anyway -- see the discussion of meaning, above -- but it's the takeaway that matters.)

for another example of an official problem in which exactly the same structure as (a) is used, check out #106 in the og verbal supplement (the sentence about inuits and aleuts).
Ron,thanks for your time and reply.
However the OA C.
In that case can you please explain the problem with C.?
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by lunarpower » Sun Mar 07, 2010 1:51 am
kaulnikhil wrote:Ron,thanks for your time and reply.
However the OA C.
In that case can you please explain the problem with C.?
as i stated up-thread, this is a fatally flawed problem. there is nothing wrong with (a) at all.

(c) is also ok. it's a little awkward to split up the construction "more efficient ... at disinfecting", but it's not, strictly speaking, incorrect.
i.e.,
The Broncos are better at physical play than the Wildcats (which is structured like (a))
is slightly less awkward / more readable than
The Broncos are better than the Wildcats at physical play (which is structured like (c))
but either could probably be ok.
the former is slightly preferable because it gives the true sense of the comparison -- better at physical play -- on the first reading. on the first reading through the latter, you get the mistaken impression of "better than the Wildcats" in general, and then you suddenly have to revise that reading when you unexpectedly encounter "at physical play" later in the sentence.

in no way whatsoever is (c) any better than (a).

i guarantee that this is not, and never was, an official problem.
the non-official problems in the "gmat sets"/1000sc are, frankly speaking, awful -- if you have doubts about one of them, you should post it here, message me (or another instructor), and verify that it's not a worthless flawed problem (like this one).
Ron has been teaching various standardized tests for 20 years.

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by nafiul9090 » Wed Nov 16, 2011 9:42 pm
the question is the mirror image of SC 18, OG 12

Plants are more efficient at acquiring carbon than are
fungi, in the form of carbon dioxide, and converting it
to energy-rich sugars.
(A) Plants are more efficient at acquiring carbon
than are fungi,
(B) Plants are more efficient at acquiring carbon
than fungi,
(C) Plants are more efficient than fungi at acquiring
carbon,
(D) Plants, more efficient than fungi at acquiring
carbon,
(E) Plants acquire carbon more efficiently than
fungi,
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