请问B选项哪里不对呢？

问题如下：

An interest rate swap is a derivative contract in which:

选项：

A.

two parties agree to exchange a series of cash flows.

B.

the credit seller provides protection to the credit buyer.

C.

the buyer has the right to purchase the underlying from the seller.

解释：

A is correct. An interest rate swap is defined as a derivative in which two parties agree to exchange a series of cash flows: One set of cash flows is variable, and the other set can be variable or fixed.

B is incorrect because a credit derivative is a derivative contract in which the credit protection seller provides protection to the credit protection buyer. C is incorrect because a call option gives the buyer the right to purchase the underlying from the seller.