This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abnormal labor, Subject name: Gynaecology & Obstetrics
[{'content': 'True about vacuum extraction of fetus: \nSelect and explain. \nA. Can be used in nondilated cervix, B. Can be used in incompletely dilated cervix, C. Used in face presentation, D. Applied 3 cm posterior to anterior fontanel', 'role': 'user'}, {'content': 'Answer: B \nExplanation: indications fetal distress in second stage Maternal distress in second stage Prolonged second stage Deep transverse arrest and persistent occipito-posterior High vacuum for second twin (refer pgno: 447 textbook of obstetrics sheila 2 nd edition)', 'role': 'assistant'}]