问题如下：
Assume a call option’s strike price is initially equal to the price of its underlying asset. Based on the binomial model, if the volatility of the underlying decreases, the lower of the two potential payoff values of the hedge portfolio:
选项：
A.decreases.
B.remains the same.
C.increases.
解释：
B is correct. When the volatility of the underlying decreases, the value of the option also decreases, meaning that the upper payoff value of the hedge portfolio combining them declines. However, the lower payoff value remains at zero.
two potential payoff 是什么？波动率不是影响因素吗？为什么不变？
