**Core Concept**
The scenario described is a classic case of potential spinal cord injury, specifically cervical spine injury, due to a high-impact trauma. The rider's inability to move, severe pain in the neck, and inability to turn his head are red flags for a possible spinal cord injury.

**Why the Correct Answer is Right**
The correct approach in this situation is to immobilize the patient's neck to prevent further injury to the spinal cord. This is achieved by keeping the patient's neck in a neutral position and not moving it until medical help arrives. The well-meaning onlookers should not attempt to make the patient sit up, as this can exacerbate the injury. The patient should be kept in a stable position, with their head and neck immobilized, to prevent any further damage.

**Why Each Wrong Option is Incorrect**
**Option A:** Trying to make the patient sit up can cause further injury to the spinal cord and is therefore incorrect.
**Option B:** Moving the patient's head or neck can also cause further injury and should be avoided.
**Option C:** This option is incomplete and does not provide a clear course of action, making it an incorrect choice.

**Clinical Pearl / High-Yield Fact**
The phrase "clear airway, breathing, circulation, immobilization, and protection of the cervical spine" (CAB-CIPS) is a useful mnemonic to remember the priority steps in managing a patient with potential spinal cord injury.

**Correct Answer: A. Immobilize the patient's neck and wait for medical help to arrive.**

✓ Correct Answer: C. He should be turned on his back and a suppo should be placed behind his neck and transpoed to the nearest hospital