Discovering the methane output of fossil fuels has been vastly underestimated, restrictions on methane emissions by researchers have been determined that could positively impact our environment more than they had previously thought.
Discovering some'g has been underestimated, (who discovered/what discovered???) restrictions................ A and B out.
A.
restrictions on methane emissions by researchers have been determined that could positively impact our environment more than they had - Incorrect as per above reason (modifier error)
B.
restrictions on methane emissions by researchers determined the positive impact on our environment more than had been - Incorrect as per above reason (modifier error)
Discovering some'g has been (vastly) underestimated, researchers have determined that restrictions (on methane emissions) could (positively) impact our environment more than previously thought. - Seems first part of sentence is clause starting with gerund (-ing modifier) and the main subject is researchers. No error but still hold it.
C. researchers have determined that restrictions on methane emissions could positively impact our environment more than - seems the weird grammatical structure (especially punctuation rules), but hold it.
D. researchers have determined that restrictions on methane emissions could positively impact our environment more
than that which was - two consecutive relative pronouns (fatal error).
E. researchers have
determined which restrictions on methane emissions could positively impact our environment more than
that - Incorrect usage of which (non-essential modifier but here the following information is crucial as a part of main clause) which changes the meaning and usage of that is additional.
Imo. C
EMPOWERgmatVerbal,
Is here in option C, does 'that....' act as relative clause?? I am sure but can you please confirm my thought as it's possible to correct the 'independent clause, independent clause' by converting any of the independent clause into phrase or relative clause.