rohitgoel15 wrote:
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.
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.