Participants of OTC derivatives are not required to publicly disclose their initial and maintenance margin positions. This statement is not a regulation that was introduced after the 2007 credit crisis. The margin requirements for OTC derivatives are typically agreed upon privately between the two parties involved in the transaction. These requirements are not publicly disclosed because they can vary widely depending on the creditworthiness of the parties, the nature of the underlying asset, and other transaction-specific factors. Therefore, there is no universal standard or requirement for the disclosure of margin positions in OTC derivatives trades. This lack of transparency is one of the characteristics that differentiate OTC markets from exchange-traded markets.

Choice A is incorrect. The Dodd-Frank Act, which was introduced in the United States following the 2007 credit crisis, mandated that standardized OTC derivatives must be traded on swap execution facilities (SEFs). This was done to increase transparency and reduce counterparty risk in these markets.

Choice B is incorrect. Central counterparty (CCP) clearing was indeed a requirement introduced for standardized derivatives transactions after the 2007 credit crisis. CCPs act as intermediaries between buyers and sellers in a derivatives contract, reducing counterparty risk.

Choice C is incorrect. Post-2007 crisis regulations also required all OTC trades to be reported to a central registry or trade repository. This measure aimed at increasing market transparency by providing regulators with detailed information about trading activities.