问题如下：
Compared to defined benefit plans, most Endowments usually have longer or shorter time horizon?
选项：
A. They have same time horizon.
B. Endowments usually have longer time horizon.
C. Defined benefit plans usually have longer time horizon.
解释：
B is correct.
Most endowments intend to have perpetual lives. However, defined benefit plans have long time horizon, but not perpetual.
c为什么不对，感觉解析c也是对的呀
