why D?

135) Refer to the accompanying figure. This economy would be operating at point B if: A) it was operating efficiently. B) the opportunity cost of making milk were higher than the opportunity cost of making movies. C) the opportunity cost of making movies were higher than the opportunity cost of making milk. D) resources that are better-suited to making movies were being used to make milk, while resources that are better-suited making milk were being used to make movies