Read the following paragraph from the section "10 Of The Most Common Book Themes." While there are countless themes found in books, there are a few that we can see in many books. These universal themes are popular among authors and readers alike because they are experiences we can relate to.

What is the main reason why the author includes this paragraph in the article?

A
to introduce the idea that there are countless themes found in books
B
to explain why universal themes are popular
C
to introduce the idea that there are some common book themes
D
to explain what universal themes are