Final answer:
In the LPO position for an L-spine oblique, the right side of the lumbar spine is best demonstrated because of the body's position relative to the image receptor.
Step-by-step explanation:
When a patient is positioned in the Left Posterior Oblique (LPO) position for an L-spine oblique, the right side of the lumbar spine will be best demonstrated. This oblique position means the patient's left posterior side is closest to the image receptor, making the right aspect of structures more prominent in the x-ray image. This is because the body is rotated such that the right side is elevated and projected without superimposition onto the left, allowing for clearer visualization.