（）是使投资组合中债券的到期期限集中于收益曲线的一点。
A．两极策略
B．子弹式策略
C．梯式策略
D．以上三种均可
参考答案：B
The boss ______ the worker how to do it, or the accident couldn’t have happened.
A．can’t have told
B．ought to tell
C．could have told
D．mustn’t have told
日本大众化报纸的兴起
