GMAT Sentence Correction (SC) | Re: As sources of electrical power, windmills now account for

dear experts,
I still did not get C ,that's how I read C

1/almost modifies verb double, so it should be as close to double as possible, only C is most close.
2/it in C refers to production, IMO, it is correct
3/ that clause is further describe what expect, seems ok
4/ the purpose of increase is to provide enough
moreover, OE for C is that :
The phrase production is expected that it will . . . makes no sense
I am confused, why no sense?
please hint .
thanks a lot
have a nice day
>_~
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