The correct answer is D) The principal adds more details to the example of a way to make learning fun.
The principal introduces Mrs. Smith by announcing that she has won the award and already begins to describe her teaching style, so answer A isn't applicable. Answers B and C don't apply either because these ideas aren't introduced at all and frankly don't make sense in this scenario. The answer is D because the principal makes a claim (that the teacher makes learning fun), and afterwards uses supporting details as evidence to support this claim by telling the story about the hats.
Hope this helps!