Boundary operator

boundary ['baʊndri]

n. 分界线;范围;（球场）边线;

bound范围 + ary 表抽象名词 → n.分界线，边界

operator ['ɑpəretɚ]

n. 经营者;操作员;电话接线员;运算符;

oper 工作 + ator表示做...工作的人或物 → n.操作人员，接线员

Great job!

干得好，干得妙！

Certainly not.

一定不是。

The only way that they can preserve their history is to recount it as sagas -- legends handed down from one generation of another.These legends are useful because they can tell us something about migrations of people who lived long ago, but none could wri

他们保存历史的唯一办法是将历史当作传说讲述，由讲述人一代接一代地将史实描述为传奇故事口传下来。