C

Reasoning: The left ureter runs down the anterior surface of psoas major; along this course it is crossed anteriorly by the gonadal vessels and by the mesentery of the sigmoid colon, and at the pelvic brim it overlies the bifurcation of the common iliac artery. It does not come into contact with the more laterally-placed quadratus lumborum muscle, making that the exception among the options [Bree et al., 1976, PMID 1251022; Kamo et al., 2021, PMID 33420862].