问题如下：
A 10-year, option-free bond pays a 7% semiannual coupon. The required YTM on this bond was 7%, but it unexpectedly increased to 7.5%. Then the price of this bond:
选项：
A. decreased.
B. remained the same.
C. increased.
解释：
A is correct.
The relationship between the price of bond and the yield of bond is negative. If the required YTM increases, the price of the bond will decrease.
发行价格是由发行时的ytm决定的，那突然后面利率变化不是对价格没有影响吗