问题如下图：
选项：
A. 
B. 
C. 
解释：
Risk free rate为什么不影响relative values of American and European call options. thanks.
NO.PZ2016031201000050 问题如下 Whiof the following circumstances will most likely affethe value of Americcall option relative to a Europecall option? A.vin are clare B.Expiration te occurs C.The risk-free rate changes A is correct.When a vinis clare Americcall option will have a higher value tha Europecall option because Americcall option holr cexercise early to capture the value of the vin expiration, both types of call options are worth the greater of zero anthe exercise value. A change in the risk-free rate es not affethe relative values of AmericanEuropecall options. 中文解析首先美式期权可以提前行权，欧式期权不可以提前行权。那什么时候美式看涨会提前行权呢？就是当未来vin够大的时候。因为发放股利会使得股票的价格下降，当股利足够大的时候，大到超过了time value(因为不提前行权，期权有时间价值， 提前行权相当于放弃了时间价值），美式看涨期权就会提前行权。如果未来没有v，美式看涨期权不会提前行权，此时美式跟欧式就一样了。所以股利对美式看涨的影响更大。B在到期日的时候，美式和欧式看涨的价值都一样，没有差别。C欧式和美式期权都会受到无风险利率的影响，不选。 分红使股票价格下跌，而call option value = S - X,S变小和提前行权有什么关系？
Expiration te occurs The risk-free rate changes A is correct. When a vinis clare Americcall option will have a higher value tha Europecall option because Americcall option holr cexercise early to capture the value of the vin expiration, both types of call options are worth the greater of zero anthe exercise value. A change in the risk-free rate es not affethe relative values of AmericanEuropecall options. C不理解需要一下
请问怎么理解A和B，不就是因为欧call不能提前赎回，expiration te不一致，所以影响Value吗？
