The listing with line of drive P-A, I-S is which listing?

• A. IN
• B. PI
• C. AS
• D. PIEX

Answer: (B)

Understanding line-of-drive listings helps translate thrust direction into a compact code. The two letters encode the path of the adjustment through two axes. The first letter shows posterior versus anterior direction, and the second shows inferior versus superior direction. If the line of drive is P-A and I-S, the thrust goes from posterior toward the anterior and from inferior toward the superior. That combination is Posterior-Inferior, abbreviated PI. So the listing is PI. Other options would correspond to different directional pairs (for example, AS would be anterior-superior), which don’t match the given directions.