GMAT Sentence Correction (SC) | Re: The best ways to store berries picked during

The best ways to store berries picked during the summer monthsis to either freeze them or have it made into jam.

(A) is to either freeze them or have it made into jam.(Ways are plural. So usage of 'is' is wrong)
(B)is to either freeze them or make them into jam.(Same as A)
(C) are to either freeze them orhave them made into jam.(Second part of either or construction is not parallel)
(D) are to either freeze them or make them into jam.(Correct)
(E)is to either freeze them and have them
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