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': 'Markedly deflexed head of baby causes which diameter to engage - \nSelect and explain. \nA. Occipitofrontal, B. Suboccipitorontal, C. Mentovertical, D. Submentovertical', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' i.e., Occipitofrontal Diameters of fetul skullAntero - posteriorDiameterMeasurement in cm (inches)Attitude of the headPresentation1. Suboccipito-bregmatic - nape of the neck to centre of bregma9.5 cms (3 3/4 ")Complete flexionVertex2 Suboccipitofrontal - nape of the neck to the anterior end of anterior fontanelle or centre of sinciput10 cms (4")Incomplete flexionVertex3. Occipito-frontal - occipital eminence to the root of nose11.5 cms (4 1/2 ")Marked deflexionVertex4. Mento-vertical - mid point of the chin to highest point of sagittal suture14 cms (5 1/2 ")Partial extensionBrow-5. Submento-vertical - junction of the floor of mouth & neck to the highest point of sagittal suture11.5 cms (4 1/2 ")Incomplete extensionFace6. Submento bregmatic - junction of the floor of mouth & neck to centre of bregma9.5 cms (3 3/4 ")Complete extensionFace', 'role': 'assistant'}]