Which of the following is most clearly an example of a theme?

a. the similarities between autobiography and creative nonfiction.
b. the division of plot into exposition, rising action, and climax.
c. people pay a high price for being overly ambitious.
d. there is a serious meaning behind the common symbol of the grim reaper.

C. People pay a high price for being overly ambitious.

Explanation:

The theme is the core idea, focus or message that an author is going to explore throughout his/her characters, storylines, and plot.  

The author conveys his/her own perspective about a particular subject, which can sometimes be universal for an audience.  In other words, the theme reveals the main meaning and intention of the story.

As in the example provided, the main theme will be the consequence people pay for being extremely ambitious.