All of the above. The initial margin for a futures contract set by a CCP is indeed influenced by both the volatility of the futures prices and the time taken by the exchange to close out a member in case of a default. The volatility of futures prices is a significant factor because it reflects the potential risk associated with the futures contract. Higher volatility implies higher risk, which would necessitate a higher initial margin to protect against potential losses. On the other hand, the time taken by the exchange to close out a member in case of a default is also crucial. If the exchange takes a longer time to close out a defaulting member, the risk of loss increases. Therefore, a longer time to close out a defaulting member would also require a higher initial margin. Thus, both these factors play a crucial role in determining the initial margin for a futures contract set by a CCP.

Choice A is incorrect. While it is true that the volatility of futures prices can influence the initial margin set by a CCP, this choice does not encompass all the factors that can potentially influence the initial margin.

Choice B is incorrect. The time taken by an exchange to close out a member in case of default can indeed impact the initial margin set by a CCP. However, similar to Choice A, this option does not include all possible influencing factors.

Choice D is incorrect. This choice suggests that none of the options listed are likely to influence the initial margin set by a CCP for futures contracts, which contradicts established financial risk management principles.