问题如下：
A swap is:
选项：
A.more like a forward than a futures contract.
B.subject to simultaneous default by both parties.
C.based on an exchange of two series of fixed cash flows
解释：
A is correct. A swap is a bit more like a forward contract than a futures contract in that it is an OTC contract, so it is privately negotiated and subject to default. B is incorrect because in a swap, although either party can default, only one party can do so at a particular time. Money owed is based on the net owed by one party to the other, and only the party owing the greater amount can default to the counterparty owing the lesser amount. C is incorrect because a swap involves an exchange between parties in which at least one party pays a variable series of cash flows determined by an underlying asset or rate.
C可以解释一下为什么？
