Final answer:
A nurse promotes correct anatomic alignment in a supine patient by placing a pillow under the patient's knees to support the natural curvature of the spine and reduce stress on joints.
Step-by-step explanation:
To promote correct anatomic alignment in a supine patient, a nurse should place a pillow under the patient's knees. This positioning helps in maintaining the natural curvature of the spine, supports the lower back, and reduces stress on the hip joint. It is important to ensure that the patient's neck is not hyperextended and that the shoulders are not adducted, as these positions could compromise anatomic alignment and possibly lead to discomfort or injury.