Answer:
b. unimportant
Explanation:
extras are usually background characters who are insignificant to the story
Famous dog trainer, Deb Tennen, writes, "Some of my best friends are dogs."
Organizing sentences around a central idea creates A SUPPORTING DETAILS.
Supporting details refers to those sentences that are used by the author to explain, clarify, describe, expand, illustrate and develop his main idea. Those sentences are usually made up of facts, statements and examples that enhance the understanding of the readers about the main idea.<span />
Lieutenant is not a part of the main clause, and it is an address to a person that is inserted into the sentence. It must be therefore separated by comas on both sides: the correct answer is a.