Final answer:
Providing spinal immobilization carries the highest risk of patient injury if performed incorrectly.
Step-by-step explanation:
The activity that would carry the highest risk of patient injury if the EMT were to perform it incorrectly is providing spinal immobilization. Spinal immobilization is an important procedure used to prevent further injury to the spine and spinal cord after trauma. If the EMT fails to properly immobilize the spine, they risk causing more damage to the patient's spinal cord, which could lead to paralysis or other serious complications.