Answer:
C. Shut down the presses printing my book
Explanation:
Since the average variable cost of producing the book is above the demand curve, the best course of action is to shut down the printing (production) of more books. The author would lose less money by shutting down operations rather than continuing production at a variable cost higher than the demand he's receiving for the books.
In economics, when profit is less than the average variable cost, firms are advised to stop production in the short run and incur economic loss on fixed inputs. This is because with continued operations, total revenue would not only be lower than total cost, but rather, would also be less than total variable cost.