Final answer:
The first sign of increased Intracranial Pressure after head trauma is typically restlessness and confusion, as these represent immediate changes in mental status due to brain injury.
Step-by-step explanation:
The first signs and symptoms of increased Intracranial Pressure (ICP) after head trauma often involve changes in mental status due to the brain's immediate response to injury. Thus, the correct answer to which symptom would appear first is C. Restlessness and confusion. These symptoms occur because the increasing pressure inside the skull can affect brain function before it leads to alterations in vital signs. While options such as bradycardia, large amounts of very dilute urine, and widened pulse pressure may emerge as the ICP continues to rise, restlessness and confusion are typically earlier indicators of increased ICP following head trauma.