This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fetal Skull and Maternal Pelvis, Subject name: Gynaecology & Obstetrics
[{'content': 'Engaging diameter in vertex, with complete extension is: \nSelect and explain. \nA. Suboccipitobregmatic, B. Mentovertical, C. Submentobregmatic, D. Occipitofrontal', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. is \'c\' i.e., Submentobregmatic DiametersMeasurement in cm (inches)Attitude of the headPresentation1. Suboccipito-bregmatic-extends from the nape of the neck to the center of the bregma9[?]5 cm (3 3/4 ")Complete flexionVertex2. Suboccipito-frontal- extends from the nape of the neck to the anterior end of the anterior fontanelle or centre of the sinciput10 cm (4")Incomplete flexionVertex3. Occipito-frontal - extends from the occipital eminence to the root of the nose (Glabella).11[?]5 cm (4 1/2 ")Marked deflexionVertex4. Mento-vertical - extends from the mid point of the chin to the highest point on the sagittal suture14 cm (5 1/2 ")Partial extensionBrow5. Sybmento-vertical - extends from junction of floor of the mouth and neck to the highest point on the sagittal suture11[?]5 cm (4 1/2 ")Incomplete extensionFace6. Submento-bregmatic - extends from junction of floor of the mouth and neck to the centre of the bregma9-5 cm (3 3/4 ")Complete extensionFace', 'role': 'assistant'}]