What structural element is affected by poe's use of both long and short sentences in the passage?

I’m your response, discuss how this part of the speech fits into the overall structure of the text and analyze how well it’s supports the authors overall purpose.

Whenever we take information from another source – whether we use the information word for word or we put the information into our own words – we must use a(n) right after where the research occurs in the paper.

American history (is, are) studying the american colonies.