Final answer:
Based on the woman's sterile vaginal exam findings (5 cm dilated, 80% effaced, 0 station), she is most likely in the active phase of labor.
Step-by-step explanation:
In this case, the woman's sterile vaginal exam reveals that she is 5 cm dilated, 80% effaced, and at 0 station. Based on these findings, the woman is most likely in the active phase of labor.
The active phase of labor is typically characterized by the cervix dilating from 4-7 cm and becoming fully effaced. The station of 0 indicates that the baby's head is at the level of the ischial spines (mid-pelvis) and is in a good position for birth.
Therefore, based on the information provided, the correct answer is C. In the active phase.