问题如下：
Which type of call bond option offers the greatest flexibility as to when the issuer can exercise the option?
选项：
A.A Bermuda call
B.A European call
C.An American call
解释：
C is correct.
An American call option gives the issuer the right to call the bond at anytime starting on the first call date.
老师，这三个区别是什么呢？有点不记得了，怎么样记更好记 呢
