Final answer:
The most appropriate method to transport the 22-year-old man after head trauma and unconsciousness is immobilizing him on a backboard.
Step-by-step explanation:
In this situation, the most appropriate method to transport the 22-year-old man who was hit in the head with a baseball and had a period of unconsciousness lasting 7 seconds is immobilizing him on a backboard (option D).
When someone experiences head trauma and unconsciousness, it is important to suspect a possible neck or spinal injury. Moving the person without proper immobilization can lead to further damage and complications. Immobilizing the person on a backboard helps to minimize movement and provides stability, reducing the risk of exacerbating any potential injuries.
The recovery position (option A) is used for a conscious person who is having difficulty breathing or vomiting. Sitting up at a 90-degree angle (option B) is not appropriate in this situation as it does not address the potential neck or spinal injury. Trendelenburg (option C) position is used to treat orthostatic hypotension and is not relevant in this case.