Best answer: A

Reasoning (concise)
• In the Duncan mechanism the placenta peels off from the margin, the rough (maternal) surface appears first and bleeding is visible immediately because blood trickles down past the edge of the placenta; it does not remain concealed behind the membranes. (Mo, 2008, PMID 18383463).  
• Because the bleeding is external from the outset, some blood may temporarily lie between the loosened placental edge and the still-attached membranes, then escape through the vagina – consistent with statement D.  
• Schultze separation (central, “shiny Schultze”) is much more common (~70-80 % of deliveries), whereas Duncan occurs in only ~20-30 % (standard obstetric texts such as Williams Obstetrics).  
Therefore the only statement that is NOT true of Duncan separation is that it is “the most common method of placental separation.”