A potential disadvantage of forward contracts versus futures contracts is:

A$.$ the extra liquidity required to cover the potential outflows that occur prior to delivery and caused by marking to market.

B$.$ the incentive for a particular party to default.

C$.$ that the buyers and sellers don't know each other and never meet.

D$.$ All of these.

E$.$ Both the extra liquidity required to cover the potential outflows that occur prior to delivery and caused by marking to market; and that the buyers and sellers don't know each other and never meet.