0.5 cun directly posterior to Quchai BL-4, 1 cun within the anterior hairline, and 1.5 cun lateral to Shangxing DU-23.

• A. BL 1
• B. BL 3
• C. BL 4
• D. BL 2

Answer: (C)

This question tests precise head point location on the bladder channel using three landmarks: a posterior relation to a nearby point, a position within the hairline, and a lateral distance from a midline point. The described spot—0.5 cun directly behind BL-3, 1 cun inside the anterior hairline, and 1.5 cun lateral to DU-23—matches the location of BL-4, Quchai. BL-4 sits just behind BL-3, near the front hairline, offset laterally from the midline by about 1.5 cun from DU-23 (which sits on the midline at the forehead). The combination of being behind BL-3, inside the hairline, and to the side of DU-23 uniquely identifies BL-4. Other bladder points lie in different local regions and would not fit these exact measurements.