Which of the following is a true statement about the way writers use sentence structure in literary works?
Sentence structure varies depending on the writer's purpose.
The structure of the writing remains the same throughout a work.
Sentence structure and sentence length are unrelated.
Writers strive to keep their sentence structure simple.

I personally believe that the very "best" answer is the first one. That sentence structure varies (and greatly does so) depending on the writer's purpose.

Explanation:

The other three answers can be "true" to a point. If, for instance the author is one of simple children's books, then that author may choose to utilize very "simple" sentence structures. thus, they may keep the same structure throughout their work. Next, sentence structure can correlate with sentence length, whereas, a very deep and thorough author may choose many prepositional phrases loaded with adjectives and adverbs to "paint" a dramatic picture to intensify the reader's imaginative thinking. Also, going back to the children's authors, many (such as elementary) writers tend to keep their sentences and structures very simplistic. Case in point.... See Spot run. See Spot jump.

Overall thought the truly "best" answer is it all depends upon their purpose. The examples I have laid out above have one thing in common, they all relate to a writer's sense of purpose. These are the reasons for my aforementioned answer. Sorry so long. Just being thorough.

Hope this helps. Good luck and God bless. Jeremy