Citadel Securities bought the unit of Morgan Stanley that focus on electronic market making for U.S. equity options. It's a move that further cements the firm's dominant role in popular derivatives, and that is today's focus on the Wall Street beat. We're going to dive into this now which whether not to Rajan of a Bloomberg News and it is amazing to see Morgan Stanley sell this business to Citadel Securities.Why would they. Because their rivalry is very, very fierce between Citadel Securities and the big ba ...