(A) do not represent a new attempt to replace fossil fuels; it
This option maintains the original sentence structure but adds a semicolon before "it." However, the use of a semicolon in this context is not appropriate. A semicolon is typically used to separate two closely related independent clauses, but "it" is not a complete sentence on its own.
(B) are not a new attempt to replace fossil fuels; the same one
This option introduces the phrase "the same one," which is redundant and awkward. The sentence already conveys the idea that plant oils were not a new attempt, so the addition of "the same one" is unnecessary.
(C) represent not a new attempt to replace fossil fuels, but one that
This option changes the verb "do not represent" to "represent not," which is an awkward and less common construction. The use of "but one that" is also unclear and does not fit well in the sentence.
(D) are not a new attempt to replace fossil fuels, but one that
Option (D) retains the original sentence structure and provides a clear and concise statement. It conveys the intended meaning without any redundancies or awkward phrasing.
(E) are not new as an attempt to replace fossil fuels; it
This option adds the word "as," which changes the meaning of the sentence. It suggests that plant oils are not new as an attempt to replace fossil fuels, but this contradicts the original sentence's meaning, which is that plant oils do not represent a new attempt.
The most effective sentence is D: