According to scientists at the University of Alaska, while the surface

i am not sure why u have said this
B looks perfect to me . comparison wise and parallelism wise

u need "over" and not "previous"

OA is B

before to post a question you have to be sure about the OA, otherwise is quite detrimental.

regards

Thank you guys. though i thought the answer is B, according to my source it's D. Now I realised my source is unreliable.

hi daagh very nicely explained but one more question,if in answer choice E in place of "PREVIOUS"..."OVER" is present then it will become correct choice means only the presence of "previous" makes it incorrect ?

REGARDS
skm

Hi skm
can u please post the your intended clause; becos, after replacing previous with over, the sentence doesn't seem to be makimg much meaning;

Hi,

According to following link, we can limit the time using in the last one year etc.. and use present perfect tense as well.

https://www.englishpage.com/verbpage/presentperfect.html

Have you been to Mexico in the last year?
I have seen that movie six times in the last month.

Thus, A and B are both grammatically correct, but B wins as B is perfect parallel to preceding clause.

after "in" , we use a number of time such as: 2 years, 3 years and it shows the future
"over" should go with a period.

"it" refers to the same thing at the previous phrase. "it" in D and E means "the suface temperature of the global" and so makes no sense.

this question tests a preposition, testing a purely grammaticaly point and so is typical of gmat sc, which normally test logic/meaning relation between entities.

Please hide the OP's question to prevent influencing answers.

Hi daagh,

There might be a mistake in your analysis. Choice A doesn't have "over the previous" that you mentioned, but "in the previous". The way I view the problems in choice A is different from yours. Please help to clarify if my understanding is incorrect/correct:

The use of "in" in this sentence is a bit confused. "in" can be understood as in "increase in" which means to become progressively greater (as in size, amount, number, or intensity). Thus, temperature cannot increase in period of time but over period of time.

How do you think?

According to scientists at the University of Alaska, while the surface temperature of the globe has risen over the last century by about one degree Fahrenheit, the surface temperature in Alaska, Siberia, and northwestern Canada has increased in the previous thirty years by about five degrees.

(A) the surface temperature in Alaska, Siberia, and northwestern Canada has increased in the previous thirty years by about five degrees not parallel with over the last century

(B) the surface temperature in Alaska, Siberia, and northwestern Canada has increased over the last thirty years by about five degrees Correct: 'while the surface temperature....has risen over the last century ,the surface temperature .....has increased over the last thirty

(C) there was an increase in the last thirty years by about five degrees in Alaska, Siberia, and northwestern Canada the beginning is not parallel with 'while the surface temperature

(D) it had increased in Alaska, Siberia, and northwestern Canada by about five degrees over the previous thirty years the beginning is not parallel with 'while the surface temperature

(E) it has increased in Alaska, Siberia, and northwestern Canada over the previous thirty years by about five degrees the beginning is not parallel with 'while the surface temperature.

daagh

Sir,Is the use of "it" in option E right or not??

i0 year" can go with simple past or present perfect because "in last 30 years" can be understood as finished or unfinished.

Hi，
I have a question.
"the surface temperature in Alaska,Siberia,and Northwestern Canada", doesn't it mean the temperature of all these three places?
if it does, why it is not "the surface temperatures of....."?
I have struggled into this question for a long time.
someone please help me explain it
thank you in advance

According to scientists at the University of Alaska, while the surface temperature of the globe has risen over the last century by about one degree Fahrenheit, the surface temperature in Alaska, Siberia, and northwestern Canada has increased in the previous thirty years by about five degrees.

(A) the surface temperature in Alaska, Siberia, and northwestern Canada has increased in the previous thirty years by about five degrees
B is better just for the preposition over
(B) the surface temperature in Alaska, Siberia, and northwestern Canada has increased over the last thirty years by about five degrees
Over is a better preposition in this context to justify the continuity.
(C) there was an increase in the last thirty years by about five degrees in Alaska, Siberia, and northwestern Canada
Kind of saying years increased by 5 degrees..wow
(D) it had increased in Alaska, Siberia, and northwestern Canada by about five degrees over the previous thirty years
There is no reason to use Had
Surface temperature is a better noun than It,because "it" may refer to surface temperature of the globe in alaska--

(E) it has increased in Alaska, Siberia, and northwestern Canada over the previous thirty years by about five degrees
Surface temperature is a better noun than It,because "it" may refer to surface temperature of the globe in alaska--

Hi AjiteshArun

Could you please add something on to this problem or any faults in my reasoning ?

Your analysis looks good.

I agree that over is better than in. Also, we can remove option C as it doesn't tell us what the increase was in and because "there was an increase" is not as direct as what the correct option uses.

Over the last 30 years sounds a little better than over the previous 30 years, but maybe that is just because I am not very familiar with something like "previous 30 years".

Hello,

Is the usage of "It" in C/D/E correct?

I would like to point out some ambiguity in the explanation of A.

It is totally fine, if you simply say "X has increased ... in the previous 30 years.". And no one would take it as excluding present.

The actual problem exists because of "over the last century" in the first clause. When you use "previous" in the second clause, it becomes unclear which period you are referring to.
(1) the last thirty years. (same to the meaning of this sentence)
(2) the thirty years prior to the last century, which is 130 years ago to 100 years ago. (most likely people will take this meaning)

"While..., ..." expresses a comparison. It will not make whole much of sense if you take the (2).