If you read original sentence..there is wrong usage of WHICH...we need WHEN to describe TIME.Hence options A/B/E =>WRONG

c) phones by using their mobile phones to make long-distance calls at night or on weekends, when
CORRECT

d) phones using mobile phones for making long-distance calls during the night or weekends, when
WRONG
PHONES USING MOBILE PHONES =>THIS IS WRONG
FOR MAKING is unidiomatic HERE.

HENCE C
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The answer will be Option "C".

It clearly rectifies the errors in the original sentence.

1) "at a time which" makes it wordy and weird. This eliminates Options A, B and E as we require a "When" here, not a "Which".

2) People can avoid toll charges "by using their mobile phones".

My reasoning is as follows, please chime in if you have any questions/comments:

present participles, after commas, modify the WHOLE preceding clause.. Thus, "using" in A/B/D modify the whole preceding clause, which distorts the intended meaning. You don't want to modify the preceding clause, you want to explain HOW people avoid toll charges.. Therefore, A/B/D are gone.

E distorts meaning by giving us a conditional "when", as if to imply that the only times they find how to avoid toll charges is WHEN using mobile phones...

C, on the other hand, clearly tells us WHAT ACTION leads to people finding how to avoid charges.. "they avoid X... by doing Y.." makes sense..

So this question is partly a modifier question, and partly a logical predication question..

I have a doubt about the usage of "when". I read somewhere it is used to denote a specific time and not general time. Can you please clarify?

I have this doubt regarding the option C and D.
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If you could recollect where you read this, it will help, because any information from non-experts might not be correct all the time, leading to bit of a confusion also.

a) phones, using their mobile phones for making long-distance calls at night or on weekends, at a time which Wrong - "which" cannot be a relative pronoun for time. Time must be "in which", "that", or "when".

b) phones, instead using mobile phones to make long-distance calls during the night of weekends, during which Wrong - "instead using" is an idiom not used correctly; "during which" is redundant and imprecise.

c) phones by using their mobile phones to make long-distance calls at night or on weekends, when Correct

d) phones using mobile phones for making long-distance calls during the night or weekends, when Wrong - "using" cannot modify phones

e) phones when using their mobile phones to make long-distance calls at night or on weekends, a time which. Wrong - "when" cannot describe phones; "which" cannot modify a time.

IMO C

A) Comma using is fine, however at times which is awful and must be replaced by when.
D) did it have COMMA before using, it would be the best!

Hi There,

I don't agree with your reasoning that

,ING is not the intended meaning here.

"Many people are finding that that they can avoid toll charges on their home phones, using BLAH BLAH BLAH"

Now How we use -ING modifier in GMAT world:

Either

(1). It should present a result of preceding clause.

OR

(2). It should be an additional information about the previous clause.

In the above sentence what you can get by the adverbial modifier starting from "-ING" is that

How people are avoiding toll charges. And the subject of the preceding clause also makes sense with the "-ING" modifier.

People, using BLAH BLAH BLAH, are avoiding toll charges.

Perfectly makes sense.

My query just for the sake of discussion on answer option (A). is :

phones,using their mobile phones for making long-distance calls at night or on weekends, at a time which

We can use "WHEN" and "Preposition WHICH" for stating time.

I know "WHEN" is much appropriate here AS PER OE from OG

"Which is the wrong relative pronoun for referring to time; substituting when for the entire phrase streamlines the sentence
and makes its meaning clear."

So is the above reasoning valid or it is the FACT that 'at the time which' is wordier than 'WHEN'.

Ex1: People use heaters in winters, at the time which people shiver in cold temperatures.
Ex2: People use heaters in winters, WHEN people shiver in cold temperatures.

So, the usage of EX1 is incorrect as per grammar/OG or it is wordier than EX2.

A,B,D - use of which (Wrong)
C- right
D- Awkward, redundant
Hope it helps:)
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In Option C, if we change this highlighted portion
phones by using their mobile phones to make long-distance calls at night or on weekends, when

and convert this option into the following sentence(this change taken from option D)
phones by using their mobile phones to make long-distance calls during the night or weekends, when

Will both the versions be correct?

c) phones by using their mobile phones to make long-distance calls at night or on weekends, when

The correct answer

one serious problem here.
look at choice e and a, " at a time which" and " a time which" are incorrect. these phrases mean:

company provide something a time
we need "during" or " at " before which so that the sentence become
company provide ... at a time

we can use time noun without preposition as in
i provide something today
but normally, we need a preposition.

so, a and e are gone.

in choice c, the correct one, "when..." clause correctly modify a noun. we normally see when clause work as an adverb but here it works as and adjective.
the time when you come is good to me
this is an example about when clause as an adjective

Hello gaitbhu,

I will be glad to help you with this one.

IMHO, the modified version of the sentence would also present the same meaning.

However, I wonder what could be the significance of this modification.


Hope this helps.
Thanks.
Shraddha
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When you see the phrase ‘at a time which’ you should realise that this is incorrect.
‘When’ is the correct preposition of time that’s to be used here.

(A) phones, using their mobile phones for making long-distance calls at night or on weekends, at a time which

(B) phones, instead using mobile phones to make long-distance calls during the night of weekends, during which

(C) phones by using their mobile phones to make long-distance calls at night or on weekends, when

(D) phones using mobile phones for making long-distance calls during the night or weekends, when

(E) phones when using their mobile phones to make long-distance calls at night or on weekends, a time which

For this reason, we can eliminate Options A, B and E.

Option D is incorrect for ‘phones using mobile phones’ which is not the intended meaning.
Plus, there is also the unidiomatic ‘for’ used in this option. Eliminate.

Option C is the best option.

Hope this helps!
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GMATNinja Just want to be crystal clear, but can "which" NOT be used to refer to time? Also, if time permits, would you please provide some feedback on my analysis?

(A) phones, using their mobile phones for making long-distance calls at night or on weekends, at a time which
(1) “which” can’t be used for time; (2) “for making” is unidiomatic – should be “to make”

(B) phones, instead using mobile phones to make long-distance calls during the night of weekends, during which
(1) “which” can’t be used for time; (2) is there anything wrong with "instead" here? Experts please help

(C) phones by using their mobile phones to make long-distance calls at night or on weekends, when
(1) “which” can’t be used for time;

(D) phones using mobile phones for making long-distance calls during the night or weekends, when
(1) “…on their home phones using mobiles phones…” – this is illogical and therefore, incorrect; (2) “for making” is unidiomatic – should be “to make”

(E) phones when using their mobile phones to make long-distance calls at night or on weekends, a time which
(1) “when” needs to modify a time, not “phones”; (2) “which” can’t be used for time;

I wouldn't make the blanket statement that "which" CANNOT be used to refer to time. It depends on the context. Here are a few examples with "which..." clauses that modify "time":

"Tim has some free time, which he feels guilty about wasting."
"Time, which was thought to be constant, is actually relative, according to some guy named Albert."
"The meeting will be postponed to a later time, which will be determined by the boss."

And here are some with "when..." clauses that modify "time":

"The meeting will be held at a time when all participants will be in town."
"I look forward to a time when pizza can be 3D-printed at home."
"I remember a time when pizza cost 10 cents a slice."

That said, you can kill both (A) and (B) for logic problems.


At first glance, it looks like the companies are providing time itself. This is nonsense, and it makes the subsequent phrase confusing, at best. A company can provide airtime, but not the abstract notion of moments passing. So while "which" can theoretically refer to time, in (A) it produces a problematic meaning. This is enough to get rid of (A).


I'm not sure what a "night of weekends" is, but it sounds pretty fun. Are we cramming multiple weekends into a Thursday night? College students certainly try, but on the GMAT, this phrase is illogical.

I hope that helps!
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