The combining form "sacr/o" is related to which of the following?

The combining form "sacr/o" specifically refers to the sacrum, which is a large, triangular bone at the base of the spine. It is an essential part of the human skeletal system, connecting the spine to the pelvis. Understanding the term "sacr/o" is crucial in medical terminology, particularly in fields related to orthopedics, anatomy, and other health sciences that involve the study of skeletal structures. In contrast, the other choices pertain to different anatomical structures and organs: the retina is related to the eye, the kidney pertains to the urinary system, and the uterus is part of the female reproductive system. Thus, "sacr/o" distinctly correlates with the sacrum, reinforcing the terminology used in various medical contexts.