Through my reading of the passage, there really isn't an emphasis on a specific sleeping disorder as each was mentioned and explained. Thus, option B becomes suitable as it relates to the many different types and variety of sleeping disorders.
The line sags like a heavy load” in "Harlem" relates to the overall feeling of "The Weary Blues" in the same way the song lyrics in “The Weary Blues” reflects a “heavy load” for the singer.
well for me it looks like a paragraph but since you say it's a sentence it's information and it's telling real facts I guess most of informational text have sentences mostly
