A. Air traffic routes over the North Pole are currently used by only two or three planes a day, but it was found by a joint Canadian–Russian study to be both feasible as well as desirable if those routes are opened to thousands more commercial planes a year.

The passive construction it was found by a joint Canadian–Russian study to be, especially followed by the conditional if, is wordy, awkward, and unclear.


B. Currently used by only two or three planes a day, a joint Canadian–Russian study has found that if air traffic routes over the North Pole are opened to thousands more commercial planes a year, it would be both feasible and desirable.

[color=#0000ff]Used by only two or three planes illogically modifies a joint Canadian–Russian study; the pronoun it has no clear antecedent.

C. A joint Canadian–Russian study, finding it to be both feasible as well as desirable to open air traffic routes over the North Pole, which are currently used by only two or three planes a day, to thousands more commercial planes a year.

The subject A joint Canadian–Russian study has no verb; to thousands more commercial planes is located too far away from to open, which it is intended to modify.

D. Although air traffic routes over the North Pole are currently used by only two or three planes a day, a joint Canadian–Russian study has found that opening those routes to thousands more commercial planes a year is both feasible and desirable.

The sentence uses correctly placed modifiers and the active voice to explain clearly what a joint Canadian–Russian study has found.


E. With air traffic routes over the North Pole currently used by only two or three planes a day, opening those routes to thousands more commercial planes a year has been found by a joint Canadian—Russian study as both feasible and desirable

The passive construction opening those routes . . . has been found by a joint Canadian–Russian study as both is wordy and unidiomatic.

Kindly suggest if there is a parallelism error as well in Option A.
Option A: Air traffic routes over the North Pole are currently used by only two or three planes a day, but it was found by a joint Canadian–Russian study to be both feasible as well as desirable if those routes are opened to thousands more commercial planes a year.
I believe but is a parallel marker in the option and is followed by a sentence it was found by a joint Canadian-russian study....., is parallelism error also one ground to reject this answer option?