Final answer:
In the LPO position, the left ureter is best visualized because it is situated away from the spine and is not superimposed by it.
Step-by-step explanation:
In the LPO (left posterior oblique) position, the ureter that is best visualized is the left ureter. The left ureter is situated away from the spine and thus is not superimposed by the spine, making it more clearly visible on an imaging study. The right ureter, on the other hand, would be positioned closer to the spine in the LPO position and hence might be obscured. The terms anterior and posterior refer to the front or back of the body, not to the positioning of the ureters; therefore, they aren't applicable to which ureter is visible in an LPO position.