A 73-year-old woman is admitted to the hospital with signifi…

A 73-yeаr-оld wоmаn is аdmitted tо the hospital with significant abdominal ascites. When she sits upright on the side of her bed, the intraperitoneal fluid accumulates in her pelvis. Which of the following sites represents the lowest extent of the female abdominopelvic cavity where this fluid will collect?