根据标准答案
B is correct. Effective duration indicates the sensitivity of a bond’s price to a 100 bps parallel shift of the benchmark yield curve assuming no change in the bond’s credit spread. The effective duration of an option-free bond such as Bond #3 changes very little in response to interest rate movements. As interest rates rise, a call option moves out of the money, which increases the value of the callable bond and lengthens its effective duration. In contrast, as interest rates rise, a put option moves into the money, which limits the price depreciation of the putable bond and shortens its effective duration. Thus, the bond whose effective duration will lengthen if interest rates rise is the callable bond, i.e., Bond #4.
(Institute 195)
Institute, CFA. 2019 CFA Program Curriculum Level II Volume 5. CFA Institute, 5/2018. VitalBook file.
关于答案中这个部分 ，对于这部分描述 不是很理解， 为什么Out of Money ，ED加长 ，是可以理解成为“赎回时间更长了的所以定性理解？
As interest rates rise, a call option moves out of the money, which increases the value of the callable bond and lengthens its effective duration.
