1997 saw the passage of the Kyoto Protocol, which aims to reduce greenhouse gases
that cause climate change, but also scientists and economists in large numbers beganattacking the effectiveness of the Protocol's reforms.
(A)1997 saw the passage of the Kyoto Protocol, which aims to reduce greenhouse gases
that cause climate change,
but also scientists and economists in large numbers began
Wrong. "but also" is awkward here. If you use "but also" to link two sentences --> the later sentence should be dependent. However, that's not the case here. The first sentence has a subject "1997", the second has a subject "scientists and economists". Both sentences have their own S and V ==> The two independent sentences can't be simply linked by a preposition ==>
Run-on error.(B) In 1997
the Kyoto Protocol was passed, aiming to reduce climate change-causing
greenhouse gases, but
it was also a year for large numbers of scientists and economists
who began
Wrong. "it" should refer to "1997". However, in B, "it" clearly refers to the Kyoto Protocol because "in 1997" is preposition phrase, not a subject.
(C) With
the Kyoto Protocol passing and aiming to reduce greenhouse gases that cause
climate change in 1997,
it was also a year when a large number of scientists and
economists had begun
Wrong. Same error as in B. "it" refers to "the Kyoto Protocol" ==> wrong.
(D) Although
1997 saw the passage of the Kyoto Protocol, which aims to reduce climate
change-causing greenhouse gases,
it was also a year when a large number of scientists
and economists began
Correct. (E)
The Kyoto Protocol was passed in 1997, and it aimed to reduce greenhouse gases
that cause climate change, but
it was also a year for scientists and economists to begin
in large numbers
Wrong. Same error as in B. "it" refers to "the Kyoto Protocol" ==> wrong.
Hope it helps.