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.
This statement is illogical I believe due to the fact of that being an opinion
It is best when drafting to proofread. I am very bad at this so I need to work on it. It is important because you need to check which sentences don't belong or what words have too many silent e's.