There is substantial evidence that certain forms of solar energy eithe

The key with this sentence is that solar energy is being talked about in the present tense and the future tense. In order to express this idea succinctly, one must coordinate these two tense. Any answer that simply uses the present or uses only the future is incorrect.


There is substantial evidence that certain forms of solar energy either now or within a few years will be economically competitive with conventional sources of heat and power.

(A) either now or within a few years will be economically competitive with conventional sources of heat and power

Use only the future tense. You cannot say either now...will be.

(B) will either be economically competitive with conventional sources of heat and power within a few years or are so now

The either implies that they are either A or B. 'A' is economically competitive. 'B' would suggest that they are something that is not economically competitive, which changes the meaning.

(C) will be economically competitive with conventional sources of heat and power either now or within a few years

Combines now with the future tense.

(D) either are now economically competitive with conventional sources of heat and power or will be so within a few years

Here we use the present tense to talk about the now and future tense will be to refers to within a few years.

(E) are either now or will be within a few years economically competitive with conventional sources of heat and power

The either now not followed by a noun phrase is awkward and confusing.
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There is substantial evidence that certain forms of solar energy either now or within a few years will be economically competitive with conventional sources of heat and power.

(A) either now or within a few years will be economically competitive with conventional sources of heat and power incorrect
Let’s separate the sentence. Either now will be economically competitive (wrong tense, it should be present tense)
(B) will either be economically competitive with conventional sources of heat and power within a few years or are so now incorrect
Not clear in meaning. This option is saying either they will be economically competitive or they won’t be.

(C) will be economically competitive with conventional sources of heat and power either now or within a few years incorrect
If solar energy is competitive now then use of “will” is not right, so sentence has to separate them. Same as option A

(D) either are now economically competitive with conventional sources of heat and power or will be so within a few years Correct
Correct tense with either (present tense) now or (future tense) within few years

(E) are either now or will be within a few years economically competitive with conventional sources of heat and power incorrect
Wordy and confusing.

A. either now or within a few years will be economically competitive with conventional sources of heat and power
This sentence separates subject from verb with awkward phrase of "either now or within a few years". Moreover it does not make any sense when we say "There is substantial evidence that certain forms of solar energy either now will be economically competitive with conventional sources of heat and power". How future will be can describe present activity.

B. will either be economically competitive with conventional sources of heat and power within a few years or are so now
Original sentence is saying either now or within a few years, this option reverses the order so incorrect.

C. will be economically competitive with conventional sources of heat and power either now or within a few years.
Use of "will be" for present situation is incorrect.

D. either are now economically competitive with conventional sources of heat and power or will be so within a few years
In this context "are" and "now" form redundant pair. We can safely ignore "now" and sentence will still make same sense. But this option is superior to other. Use of "so" in or section to correctly refer to verb in either construction is perfect.

E. are either now or will be within a few years economically competitive with conventional sources of heat and power
In this context "are" and "now" do not forms redundant pair, however as such will mean "are" is applied to both "either as well as or construction" which I will say is grammatically flawed. Moreover there is nothing in either construction that refers to verb of or construction.

I think redundancy is still allowable but grammatical mistakes are not, please correct me if I am wrong.

So I will go with D.

[quote="rohitgoel15"]There is substantial evidence that certain forms of solar energy either now or within a few years will be economically competitive with conventional sources of heat and power.
(A) either now or within a few years will be economically competitive with conventional sources of heat and power
(B) will either be economically competitive with conventional sources of heat and power within a few years or are so now
(C) will be economically competitive with conventional sources of heat and power either now or within a few years
(D) either are now economically competitive with conventional sources of heat and power or will be so within a few years
(E) are either now or will be within a few years economically competitive with conventional sources of heat and power


I see the problem with C. "Now" signals the present tense of the verb "be."
If C was like "will be economically competitive with conventional sources of heat and power either shortly or within a few years then C would be the answer.

There is evidence that certain forms of energy either are now competitive..............or will be in few years

There is substantial evidence that certain forms of solar energy either now or within a few years will be economically competitive with conventional sources of heat and power.

(A) either now or within a few years will be economically competitive with conventional sources of heat and power
(B) will either be economically competitive with conventional sources of heat and power within a few years or are so now
(C) will be economically competitive with conventional sources of heat and power either now or within a few years - we cannot say 'will be competitive now'.....thats wrong tense
(D) either are now economically competitive with conventional sources of heat and power or will be so within a few years - 'so' is for the task
(E) are either now or will be within a few years economically competitive with conventional sources of heat and power

Hi all,
the trap is that C looks very attractive. but in C either X or Y are not paralel.
Unlike D (either + auxiliary verb + time) + (or + auxiliary verb + time), C is not parallel: either now (adjective) or within (preposition)

hope it helps.
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The sentence means to say that --- There is substantial evidence that certain forms of solar energy either now will be economically competitive or within a few years will be economically competitive with conventional sources of heat and power. You can see the incongruity of the theme --- now will be economically competitive. So any choice that has – now will be economically competitive can be eliminated

Second thing is the adherence to //ism of correlative conjunction.


A. either now or within a few years will be economically competitive with conventional sources of heat and power --- fouls on ---now and will be ---factor. drop

B. will either be economically competitive with conventional sources of heat and power within a few years or are so now --- be economically is not a full verb . So its placement after either is not correlatively // with or are so now. – drop.

C. will be economically competitive with conventional sources of heat and power either now or within a few years ---- fails on now and will be factor. ---drop

D. either are now economically competitive with conventional sources of heat and power or will be so within a few years …correct choice. –no now and will be problem and maintains correlative //ism

E. are either now or will be within a few years economically competitive with conventional sources of heat and power …… -are either now or will be within a few years - is not correlatively parallel.
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Tough ONE: Initially I was not able to identify error in A, but when I checked variations in all other choices I managed to identify what creator wants us to do.

expended version : now will be or within few year will be -- now will be is not correct -- now represent present tense. Thus, we cant use future tense will.

858. There is substantial evidence that certain forms of solar energy either now or within a few years will be economically competitive with conventional sources of heat and power.
(A) either now or within a few years will be economically competitive with conventional sources of heat and power
(B) will either be economically competitive with conventional sources of heat and power within a few years or are so now -- parallelism error.
(C) will be economically competitive with conventional sources of heat and power either now or within a few years -- modifier error
(D) either are now economically competitive with conventional sources of heat and power or will be so within a few years -- Technically correct construction.
(E) are either now or will be within a few years economically competitive with conventional sources of heat and power -- Parallelism error.

Request you not to write your queries/answers/opinions in question window. It prevents ppl from analysing the question. The whole purpose of GMAT Club forum goes wasted by doing so.

let's analyze the question:
there is evidence
certain forms of SE will be economically competitive.
when will be? either now, or within a few years.

Error analysis:
although in A both "now" and "within few years" looks parallel, the verb that comes after that does not make sense with both entities.
SE now will be economically competitive...
if we are talking about the present, then why do we not use present simple? Moreover, now or within looks to me incorrectly placed.

(A) either now or within a few years will be economically competitive with conventional sources of heat and power
as mentioned above.

(B) will either be economically competitive with conventional sources of heat and power within a few years or are so now
the verb before "either" is "will". the second entity of the idiom either x or y doesn't make sense with the verb. thus incorrect.

(C) will be economically competitive with conventional sources of heat and power either now or within a few years
again, same mistake. will be now...nope.

(D) either are now economically competitive with conventional sources of heat and power or will be so within a few years
either are or will be - looks ok. worded ok, looks like we have a winner.

(E) are either now or will be within a few years economically competitive with conventional sources of heat and power
the same mistake as in B. the main verb is "are", then we have another verb "will be", are will be? nope!

D is the winner.

B changes the meaning, suggesting that the alternative resources will be economically competitive or may not be. Is too confusing
A combines the present and future tenses, not correct.
C does the same
E is too wordy

D is the correct option

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