Which of the Below Does NOT Involve a Function of the Clearinghouse

Which of the below does NOT involve a function of the clearinghouse?

A) One functions is to guarantee that the two parties to the transaction will perform.
B) When someone takes a position in the futures market, the clearinghouse takes the same position and agrees to satisfy the terms set forth in the contract.
C) The clearinghouse makes it simple for parties to a futures contract to unwind their positions prior to the settlement date.
D) The clearinghouse interposes itself as the buyer for every sale and the seller for every purchase.