Ingrid and Her Sister-In-Law Jenna Both Began Labor at the Same

Ingrid and her sister-in-law Jenna both began labor at the same time this morning. It is Ingrid's first birth and Jenna's third. Which of the following will MOST LIKELY be true of their deliveries?

A) They will happen at about the same time because most women experience very similar lengths of labor.
B) Ingrid's will be shorter because this is her first birth, and it is Jenna's third.
C) Ingrid's will be longer because this is her first birth, and it is Jenna's third.
D) There is no way to tell whose will be shorter or longer because length of labor is highly variable from woman to woman.