Final answer:
The supine position is best to demonstrate an abdominal aortic aneurysm, as it allows clear visualization of the aorta lying on the back with limbs at the sides.
Step-by-step explanation:
The position that would best demonstrate an abdominal aortic aneurysm is the supine position. An abdominal aortic aneurysm (AAA) is a dilation in the lower part of the aorta, the major blood vessel that supplies blood to the body. When imaging the abdomen, the supine position, where the person is lying on their back with both upper and lower limbs touching their sides, could provide a clear view of the aorta without interference from other structures or gravity. This position allows for the use of ultrasound or computed tomography (CT) to visualize the aneurysm effectively.