Bourbon, created from a mixture based mostly on corn, and Rye whiskey, consisting of at least 50% rye, is distilled to contain no more than 80% alcohol per volume and is poured into new oak barrels for the aging process, as doing so complies with federal regulations.
A.
is distilled to contain no more than 80% alcohol per volume and is poured into new oak barrels for the aging process, as doing so
IncorrectB.
is poured into new oak barrels for the aging process and is distilled to contain no more than 80% alcohol per volume and, as to do so
IncorrectC. are distilled to contain no more than 80% alcohol per volume and are poured into new oak barrels for the aging process, as
it IncorrectD.
are distilled to contain no more than 80% alcohol per volume and are poured into new oak barrels for the aging process, as doing so CorrectE. are distilled to
contain more than 80% alcohol per volume and are poured into new oak barrels for the aging process, as to do so
IncorrectPOE -
Bourbon,....., and Rye whiskey,..., ............... - verb should be are
Eliminate A & B
doing so or to do so - correct idioms; Eliminate C
In E missing no that changes intended meaning
So, Answer D