Final answer:
The factors contributing to cord prolapse include a small fetal head and an unengaged presenting part, which can allow space for the umbilical cord to prolapse.
Step-by-step explanation:
The maternal and fetal factors contributing to cord prolapse are typically those that prevent the fetal presenting part from adequately occluding the internal os (opening) of the cervix, which can allow the umbilical cord to prolapse around or beside the presenting part. The correct answer to the question is b) Small fetal head, vertex presentation, and engaged presenting part. This is because a small fetal head may not block the cervix adequately, and an unengaged presenting part, common in malpresentations such as breech, can also lead to space through which the cord can prolapse. Factors like a large fetal head and an engaged presenting part would more likely help in preventing a cord prolapse by blocking the internal os more effectively.