Sentence Correction

Scientists now theorize that the phenomenon of global warming is a result as much of natural climate fluctuation than of pollutants contributed by humankind.
A
is a result as much of natural climate fluctuation than of
B
is a result as much of natural climate fluctuation as do
C
is a result as much of natural climate fluctuation as of
D
is as much a result of natural climate fluctuation as it is of
E
was a result as much of natural climate fluctuation as of

This is a quetion from BellCurve, the answer is D. But I don't understand why C is incorrect. Can someone help explain it?

Plus, is there any difference between "sth as many/much as" and "as many/much sth as"?

Thanks for help!