问题如下：
Is it true that the expected payoff of the derivative can be discounted at the risk-free rate plus a risk premium?
选项：
A. No, because a conbination of a derivative and the underlying can produce a risk-free asset.
B. Yes, because most investors are risk averse, they require a risk premium.
C. No, because most investors are risk neutrality, they do not need a premium.
解释：
A is correct. The expected payoff of the derivative can be discounted at the risk-free rate, because a derivative can be combined with an asset to produce a risk-free position and the derivative price can be obtained by assuming that the investor is risk neutral.
C is incorrect because most investors are risk averse, however the investor's risk aversion does not affect the derivative price.
老师，我不太能理解这道题的解释，太抽象了，可以举例子吗？比如用mbs作为一个衍生品举例，为什么未来的pay off要用无风险利率来折现？之前不是说需要加一个信用风险溢价spread吗？
