Answer:
This is an infinitive.
Explanation:
A gerund is a verb used as a noun; "suggesting" is not used as a noun in this case.
For this item, I will go with the first option, "What is the authors purpose in writing this piece?". This is important to ask in first read of a multi-draft reading process because if we desire to know something about the subject, it is important to note how the reading material would be of help to us and we know that by the purpose of the author.
I absolutely love Shakespeare so i know for a fact the answer is d with no doubt about it.