问题如下：
Which of the following is most likely to raise the required YTM?
选项：
A.Call option.
B.The floor of a floating exchange rate.
C.Put option.
解释：
A is correct.
Call options are good for the issuer and raise the required YTM. On the contrary, a put option or a floor protects favor the bondholder, thus decreasing the required YTM.
老师，这题目还是不明白，想要提高YTM,不应该是卖出一个含权债券，因为市场的利率不断增加，对于投资者拿到的钱会更多呀
