This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Transverse Lies, Oblique Lies and Shoulder Presentations , Subject name: Gynaecology & Obstetrics
Presenting part most commonly encountered in longitudinal lie is - 
Select and explain. 
A. Brow, B. Vertex, C. Face, D. Hand
B: Vertex
Answer: B: Vertex 
Explanation: Ans. is 'b' i.e., Vertex o The presenting part is defined as the part of the presentation which overlies the internal os and is felt by the examining finger through the cervical opening.o Thus, in cephalic presentation, the presenting part may be vertex (most common), brow or face, depending upon the degree of flexion of the head.o Similarly, the fetal legs in a breech presentation may be flexed (complete breech), extended (frank breech) or a foot may be present (footling).Preponderance of Lie, presentation and presenting partLiePersentationPresenting Part of CephalicLongitudinal (99.5%)Cephalic (96[?]5%)Vertex-(96%)Transverse Oblique UnstableBreech (3%), Shoulder (0.5%)Brow face (0[?]5%)