Thor Would Like to Get His Son to Read More

Thor would like to get his son to read more without compromising the child's intrinsic motivation to read. Which of the following strategies could best achieve this?

A) Give the child a strict deadline by which time he must have read a set number of books.
B) Set up a competition with other kids in the neighborhood to see who can read the most books.
C) Create a schedule of how many hours the child should be reading each day and then closely supervise him to make sure he sticks to the schedule.
D) Give the child a new book for every book that he reads and make it clear that he is doing a good job of reading the books.