HELP!! Why should you use a variety of sentence structures in your writing?

A: Using a variety of sentence structures helps a piece of writing to be more interesting and smooth and less monotonous. Complex sentences help to show the connections among ideas and sentences.

B: Using a variety of sentence structures makes a piece of writing more complicated to read. This makes the writer appear to be more educated and artistic in order to impress others.

C: Using a variety of sentences structures makes a piece of writing more informal. This makes the writer have a more casual tone with which to persuade readers.