Which Statement Related to Fetal Positioning During Labor Is Correct

Which statement related to fetal positioning during labor is correct and important for the nurse to understand?

A) Position is a measure of the degree of descent of the presenting part of the fetus through the birth canal.
B) Birth is imminent when the presenting part is at +4 to +5 cm below the spine.
C) The largest transverse diameter of the presenting part is the suboccipitobregmatic diameter.
D) Engagement is the term used to describe the beginning of labor.