Answer:
The correct parallel structure is
Public speaking, writing e-mails, and designing presentation visuals are difficult for many people.
Explanation:
Parallel Structure in English Grammar:
Parallel structure in English grammar is known as parallelism. It is a technique of writing or speaking in which sentences have identical grammatical structure like
Subject + verb structure can been seen in the following example
They play, they write and they walk daily.
So in our case this sentence " Public speaking, writing e-mails, and designing presentation visuals are difficult for many people." has same grammatical structure as each clause is starting with verb+ing like speaking, writing and designing.
