(B) make it possible to study, in greater detail, the effects of calefaction, or warming, of a river than ever before

This is a subtle case of a misplaced modifier. We need "than ever before" to be directly linked to "study in greater detail"

Here it sounds more like we're saying "The effects of calefaction or warming of a river than ever before" which creates a disconnect from the intended comparison.

The excessive use of commas to create modifiers within modifiers is also awkward, though this is a secondary problem.

Placement of phrases is an important factor, and bears a higher priority than style or wordiness.

IMO C

(A) makes it possible to study the effects of calefaction, or warming, of a river in greater detail than ever before (Techniques - should be make)
(B) make it possible to study, in greater detail, the effects of calefaction, or warming, of a river than ever before (in greater detail is wrongly placed)
(C) have made it possible to study in greater detail than ever before the effects of calefaction, or warming, of a river ---- Correct
(D) make possible the study of the effects of calefaction, or warming, of a river in greater detail than it ever was before (make possible the study is wrong)
(E) has made it more possible than ever before to study in greater detail the effects of calefaction, or warming, of a river ---- (Techniques ----should be have)

Can anybody explain that why is option B not correct and C is the answer.

Yes i like the post. I will like to add one more thing -

We use simple present tense for - facts, habitual action.
e.g Sun rises in the East ( a fact)
Ron jogs 3 miles every morning (a habit)

I don't see any of these cases w.r.t "New techniques in thermal-scanning photography".
The statement is telling me that such new techniques which don't exist sometime in the past now exist and are useful to study the effects of blah blah in greater detail. The use of simple present tense make will NOT be correct.

blah blah = the effects of calefaction, or warming, of a river

Hence I go with present perfect - "have made it possible to study". C it is.

can you guys please clarify as to what does "IT" refers to in option C.

have made it possible to study in greater detail than ever before the effects of calefaction, or warming, of a river

Here the "it" is used as a pronoun to anticipate "the effects..."

"have made the effects of (...) possible to study in greater detail..."

The pronoun is introduced before the antecedent.

eg. I love it when the sky is clear.
or, Your abstruse approach makes it difficult to understand the solution.

We are describing the antecedent using a pronoun modifier. This is perfectly acceptable.

New techniques in thermal-scanning photography, a process that records radiation from surface areas, makes it possible to study
the effects of calefaction, or warming, of a river in greater detail than ever before.
(A) makes it possible to study the effects of calefaction, or warming, of a river in greater detail than ever before
phrase "in greater detail than ever before" modifies the verb and should be placed right next to it
(B) make it possible to study, in greater detail, the effects of calefaction, or warming, of a river than ever before
"in greater detail than ever before" should not be separated. Otherwise, we need another subject and a verb to make it work.
(C) have made it possible to study in greater detail than ever before the effects of calefaction, or warming, of a river. Correct
(D) make possible the study of the effects of calefaction, or warming, of a river in greater detail than it ever was before. They key here, I believe, "the study in greater detail" is inferior to "to study in greater detail. A study that is more detailed than ever before would have made D more attractive than it is now.\

(E) has made it possible than ever before to study in greater detail the effects of calefaction, or warming, of a river subject-verb agreement

B) Techniques is a plural term. Obviously it requires a plural verb make.

C) Now the substance of the sentence is that new techniques made it possible in the past, make it possible presently and will make it possible in the future to study in greater detail. The right tense to denote such a day-to-day affair is the use of simple present. Hence make it possible rather than have made it possible.
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between B & C,
present perfect makes a better sense, however, apart from tense I can not realize how we can rule out B due to placement of comparative forms of which I'm suspicious.

By rule of grammar, - make it possible - is not ungrammatical although -have made it possible - conveys the meaning of the context better; Secondly the word order in B is erroneous with - than ever before - modifying the warming of a river. It should rightly modify - in greater detail - as in C.
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New techniques is a plural subject and demands a plural verb. So, A and E are out.
The problem with D is the ambiguous "IT" at the end because it seems to be referring to something but the meaning is not complete.
Among B and C: Why does in greater detail need to be within commas? Redundancy. Also it seems like in greater detail is not necessary to complete the meaning of the sentence. In other words like a which or a that its a limiting phrase.
Finally if you look at B without the limiting phrase: make it possible to study the effects of calefaction, or warming, of a river than ever before. Does this even make sense? The phrase "than ever before" has to be preceded by the action it modifies which is "in greater detail". So, B is clearly WRONG.

Choose C and move on.

(A) makes it possible to study the effects of calefaction, or warming, of a river in greater detail than ever before
(B) make it possible to study, in greater detail, the effects of calefaction, or warming, of a river than ever before
(C) have made it possible to study in greater detail than ever before the effects of calefaction, or warming, of a river
(D) make possible the study of the effects of calefaction, or warming, of a river in greater detail than it ever was before
(E) has made it more possible than ever before to study in greater detail the effects of calefaction, or warming, of a river

C is the answer - clear meaning and comparison usage of 'greater...than'

A & E - wrong - because of subject verb
B - wrong because greater ... than are not connected
D-wrong - bad structure - 'make possible ????'

Quite a straightforward one I'd say. Firstly, techniques being the subject requires that the verb be plural. Given this situation, you can eliminate options A and E. Among those that remain:

(D) make possible the study of the effects of calefaction, or warming, of a river in greater detail than it ever was before
Unnecessarily wordy and awkward.

(B) make it possible to study, in greater detail, the effects of calefaction, or warming, of a river than ever before
Awkward construction with the numerous commas.

(C) have made it possible to study in greater detail than ever before the effects of calefaction, or warming, of a river
Best option. It conveys the point crisply.
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New techniques in thermal-scanning photography, a process that records radiation from surface areas , have made it possible to study in greater detail than ever before the effects of calefaction, or warming, of a river

With (C) for the errors highlighted above...
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Well ,I am still not convinced by the OA, and confused between B and C.
Yes, I agree that have does appear nice.
BUT as per my knowledge in GMAT it is preferred to use Simple tense as much as possible unless the sentence is not grammatically wrong AND perfect tenses are generally not used.
Can anybody please correct me..??

suramya26



I am afraid you are wrong to a very great extent. If you go with such notions into the exam, you will end up only getting the short end of the stick.
There are three simple tenses in grammar. i.e. a simple past, a simple present, and a simple future. It is not clear which one you are referring to.
The right perspective is that one should use the correct tense as the context demands. I do not think there is any preference, said either explicitly or implicitly by GMAT in the choice of the tense.
It must also be noted that most of the higher level questions involve the use of past and present perfect tenses or the use of the third conditionals in GMAT
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Thanks a lot sir,
Sir , the tell me whether my reasoning is wrong??
The reason for which C is the correct answer is because the option stresses on the effect of new technologies
And this the effect is still IN THE PRESENT

Suramya

Hi

Don’t you feel that there is no difference between B and C as far as new techniques are concerned? C is better because of the superior word order; in B, the placement of ‘than ever before’ after the river is changing the meaning.
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let's use the e-gmat 3 step process...

1. understand the meaning
new techniques allow to study smth in more details than it was possible before
what to study? the effects of C or W of a river.

2. error analysis
first error that jumps in the eyes is the SV agreement error. The noun is plural "techniques", while the verb is singular "makes".
A and E make the same mistake.
Since the techniques were not always present, I think it is more appropriate to use the present perfect - an action that happened in the past, but whose effects are still felt in present.



a. makes it possible to study the effects of calefaction, or warming, of a river in greater detail than ever before
as discussed above

b. make it possible to study, in greater detail, the effects of calefaction, or warming, of a river than ever before
while make does not make 100% incorrect this answer choice, the placement of "than ever before" definitely makes it incorrect.

c. have made it possible to study in greater detail than ever before the effects of calefaction, or warming, of a river
looks good!

d. make possible the study of the effects of calefaction, or warming, of a river in greater detail than it ever was before
it does not make possible the study. it made possible to study in more details. this option changes the meaning of the sentence.

e. has made it more possible than ever before to study in greater detail the effects of calefaction, or warming, of a river


C looks to be the winner.