the advanced state of civilization reached by the spiro people as evidenced by artifacts found in the spiro mound

Look at the passages where the author describes the isolation and insanity that dr frankenstein has

Read and you will find the answer

The answer is indeed b

1) if the main idea is to show the sequence of events, a cause-and-effect style of writing will be used.  2) if the main idea is to show why one product or idea is better than another, the basic points of each side will be compared and contrasted.  3) if the main idea is to present opposing viewpoints, the pros and cons of each side will be discussed.  4) if the main idea is to draw special attention to an important cause or event, various examples will be provided.  5) if the main idea is to define a certain term or concept, various examples and explanations will be provided.