Answer: C. chronological.

Explanation: When organizing the ideas of a speech we need to pay attention to certain elements, like the audience, the subject and the main function of the speech, in the given example, we know that Sarah wants to write a speech about dogs, mor specifically, about training dogs, and she wants the purpose of the speech to be teaching her audiens how to train a dog, so, according to those elements, she should use a chronological style to organize the ideas, in this way she will be able to explain all the necessary steps to train a dog.