问题如下：
An option has a strike price of USD 50. A cash dividend of USD 0.50 is announced with an ex-dividend date before the end of the life of the option. What effect does this have on the strike price?
解释：
There is normally no effect on the strike price when a cash dividend is declared. An exception may be made when the dividend is large-more than 10% of the stock price.
为什么大于10%可能是个exception？
