Final answer:
The appropriate intervention for a nurse assessing a preadolescent child for scoliosis is to perform a complete physical examination and observe the child's posture.
Step-by-step explanation:
The appropriate intervention for a nurse assessing a preadolescent child for scoliosis is to perform a complete physical examination and observe the child's posture (A). Excessive vertebral curves can be identified by observing the vertebral profile from the side and behind, checking for kyphosis or lordosis. When the child bends forward, difficulty in bending directly forward and a lack of levelness between the right and left sides of the back indicate the presence of scoliosis.