A woman is 7 cm dilated, and her contractions are 3 minutes apart. When she begins cursing at her birthing coach and the nurse, what does the nurse assess as the most likely explanation for the woman's change in behavior?

The contractions have increased from mild to moderate intensity.

Labor has progressed to the transition phase.

She lacked adequate preparation for the labor experience.

The woman would benefit from a different form of analgesia.