Question

which sentence or sentences have correct parallel structure?
lily, after you confirm that our mailing list is up to date, bryan will stuff
the envelopes, will address them, and drop them off at the post office.
lily, after you confirm that our mailing list is up to date, bryan will stuff
the envelopes, address them, and drop them off at the post office.

Explanation:

To determine correct parallel structure, we check the verb forms in the series of actions. In the second sentence, "stuff the envelopes", "address them", and "drop them off at the post office" all use base - form verbs (in the context of the future - tense construction with "will" for the overall action, the actions after "will" should be parallel in form). The first sentence has "will stuff", "will address", and "drop" (the "will" is inconsistent in the last verb as it's omitted in a non - parallel way). So the second sentence has correct parallel structure.

Answer:

The second sentence (Lily, after you confirm that our mailing list is up to date, Bryan will stuff the envelopes, address them, and drop them off at the post office) has correct parallel structure.