Answer:
Complete sentence.
Explanation:
A sentence fragment is a clause or a group of words that are part of a sentence but do not form or make a complete sentence. They can be best identified by the structure or composition of the sentence, as it will miss either a subject, a verb or an object, or a complete thought. Even if it contains both a subject and a verb, it can sometimes be a sentence fragment.
The given sentence "the author researched the Great Depression" is a complete sentence as it has all the necessary elements of a complete sentence.
Answer:
I would like to say a and b
Yes, it should always be placed.
A research paper is fact and nothing but the fact. A research paper is just giving information about a topic. However, rhetorical questions are used to persuade the reader to believe or agree with something, mainly in a discursive essay; but in a research paper, you aren't persuading, you are educating.