请问一下，这道题目答案到底应该选什么？书上是选C，both；但是“有问必答”上说选A。并且麻烦解释一下，谢谢！
书上答案原文：
“7 C is correct. Both statements are correct. The expected future payoff is calcu
lated using risk- neutral probabilities, and the expected payoff is discounted at
the risk- free rate.”
Jack Sun · 2021年09月24日
请问一下，这道题目答案到底应该选什么？书上是选C，both；但是“有问必答”上说选A。并且麻烦解释一下，谢谢！
书上答案原文：
“7 C is correct. Both statements are correct. The expected future payoff is calcu
lated using risk- neutral probabilities, and the expected payoff is discounted at
the risk- free rate.”
我看错了，有问必答的答案是对的。我问的是第9题，答案是A，能否解释一下，谢谢！ 9 Which of Sousa’s reasons for the decrease in the value of the interest rate option is correct? A Reason 1 only B Reason 2 only C Both Reason 1 and Reason 2