My best guess and answer is:
D
because the author is trying to reach out to his viewers or readers to understand and try to find out if they have a lack of decency in their own society they are living in.
Hope this helps!!
C. You need a comma when the sentence changes subjects from humans to bottlenose dolphins.
The answer would be:
The biography uses a chronological structure; "Marian Anderson Sings" uses flashbacks to narrate the events.
