The correct answer is D. The author gives examples of wild horses being trained and then adopted by the U.S. Marine Corps.
Step-by-step explanation:
In the text presented the author states the way the U.S. Marine Corps, which is part of the Armed Forces in the U.S. decided to adopt a wild horse in 1988 and as a result of the positive performance of this horse continued adopting many other wild horses. For supporting the main idea of the text, which is that wild horses can be adopted and trained the author mainly explains to the audience the way in which the first wild horse was adopted and the performance of it as part of the Mounted Color Guard by providing details about how quickly the horse became an important part of the parades and unexpectedly was not afraid in situations with loud noises.
This shows the author aims at showing to the audience it is possible to adopt horses and integrate them to the Marine Corps by presenting the story of one of the horses or by giving an example of wild horses being trained and then adopted by the U.S. Marine Corps, as this is a fact and shows it is possible wild horses can be part of the Armed Forces.