Final answer:
To protect the patient's spine when moving him lengthwise, the head should be supported to maintain the alignment of the head, neck, and spine.
Step-by-step explanation:
To protect a patient's spine who must be moved lengthwise on the ground next to his automobile, the correct position would be d. Head supported. This would ensure that the spine remains as neutral as possible and avoids any additional strain or injury. When moving a patient in such a situation, it's crucial to maintain the alignment of the head, neck, and spine to prevent exacerbating any potential spinal injuries. A body that is lying down is described as either prone or supine, where prone describes a face-down orientation, and supine describes a face-up orientation. These details are critical in positioning the patient correctly for both assessment and transportation to a medical facility.