There are four essential components of labor. The first is the passageway. It is composed of the bony pelvis and soft tissues. What is one component of the passageway?

Cervix.

Explanation:

The process of the child birth and the delivery of the baby from the mother's womb shows the labor. The labor process is completely divided into the four stages.

The passageway is the first stage of labor. This is further divided into the early labor and active labor. The vagina and cervix are the main component of the first phase and consist of the soft tissue. The birth canal is formed by the together of the vagina and cervix.

Thus, the answer is cervix.