Final answer:
The finding of a slit-shaped cervical os in a nulliparous woman like Ms. Horter can be explained by infection with the human papillomavirus (HPV).
Step-by-step explanation:
The finding of a slit-shaped cervical os in a nulliparous woman like Ms. Horter can be explained by infection with the human papillomavirus (HPV). Research has shown that cervical cancer, which is often caused by HPV, can alter the shape of the cervical os. In this case, the HPV infection has likely caused changes in the cervical tissue, resulting in the slit-shaped os. Other factors in Ms. Horter's history, such as early onset of menarche, multiple sex partners, or elective abortion, may have an impact on her risk of HPV infection but are not directly related to the observed finding.