In preparation for the cold winter months,
it was the usual custom for prehistoric people to gather and preserve, with smoke or by salting it, as much meat that they could during the summer.
(A) it was the usual custom for prehistoric people to gather and preserve, with smoke or by salting it,
as much meat
that they could during the summer.
Wrong. "as much ... that they could" is not idiomatic --> correct syntax is "as much.... as....."
In addition, "
gathering" and "
preserving" MUST be
SEPARATED --> See explanation in D.
(B) prehistoric people usually gathered
as much meat
as they could during the summer, preserving it
either by smoking or salting Correct. "as much .... as" is good. "either by smoking || salting" --> keeps parallel structure.
(C) it was the usual custom of prehistoric people to gather and preserve,
either with smoke or
by salting, as much meat that they could during the summer
Wrong. "either X or Y" --> X and Y must be parallel, but "with smoke" and "by salting" are not parallel.
In addition, "
gathering" and "
preserving" MUST be
SEPARATED --> See explanation in D.
(D) prehistoric people had the usual custom of
gathering and preserving as much meat,
either by smoking or salting it, as they could during the summer
Wrong. "
gathering" and "
preserving" MUST be
SEPARATED. Correct meaning is "
gather as much meat as they could" and "
preserve it either by smoking or salting". D, however, means (1) people gather meat either by smoking or salting + (2) preserve meat either by smoking or salting <-- totally wrong meaning.
(E) it was usually that prehistoric people would gather and preserve as much meat as they could,
which was either smoked or salted during the summer
Wrong. "which" is wrong.
Hope it helps.