B

Progressive sperm motility is the parameter that correlates most closely with the ability of spermatozoa to traverse the female genital tract and achieve fertilization, and the WHO semen manual therefore highlights the ≥40 % total/≥32 % progressive motility cut-offs as the key thresholds for normal fertility potential [WHO Manual, 2010; Villani et al., 2022, PMID 34723422; Jedrzejczak et al., 2008, PMID 17651398].