问题如下：
Steele Ferguson, a senior analyst at Samuel, is reviewing three fixed-rate bonds issued by a local firm, Pro Star, Inc.
The bond that would most likely protect investors against a significant increase in interest rates is:
选项：
A.Bond #1.
B.Bond #2.
C.Bond #3.
解释：
The bond that would most likely protect investors
against a significant increase in interest rates is the putable bond, i.e.,
Bond #3. When interest rates have risen and higher-yield bonds are available, a
put option allows the bondholders to put back the bonds to the issuer prior to
maturity and to reinvest the proceeds of the retired bonds in higher-yielding
bonds.
我知道putable bond 是保护投资者的，但是只在利率下降的情况下，价格有个底线啊，课上putable的图，本题题干说的是利率上升，应该跟callable有关啊？
