单项选择题

A private agreement between two parties to exchange a series of future cash flows, with at least one of the two series of cash flows determined by a later outcome, is best characterized as a (n) :

A.<TABLE border=0 cellSpacing=0 cellPadding=0 width="90%"><TBODY><TR><TD vAlign=top>A. swap. </TD></TR></TBODY></TABLE>
B.<TABLE border=0 cellSpacing=0 cellPadding=0 width="90%"><TBODY><TR><TD vAlign=top>B. futures contract. </TD></TR></TBODY></TABLE>
C.<TABLE border=0 cellSpacing=0 cellPadding=0 width="90%"><TBODY><TR><TD vAlign=top>C. over-the-counter contingent claim.</TD></TR></TBODY></TABLE>