In order to be able to answer this, we'd need to know what book it is you're reading, as well as the answer choices as the question asks "which of the following best" meaning that they want you to choose the best answer from the choices they’re giving you.
Just in my opinion:
1. True
2. True
3. False
4. True
5. True
6. True
Motif is a reoccurring theme or idea shown with symbolic value, and theme is a general concept that the author wants readers to see. These both help readers understand or grasp a better understanding of plot, so the answer is c.