双输入双输出

The children went in two by two. 孩子们两个两个地进去。

The children came in two by two (= in groups of two). 孩子们一对一对地走了进来。

Lakka-trees ripen two by two And mandarin-ducks die side by side. 梧桐相待老, 鸳鸯会双死;

They were seaed two by two, with six-foot-tall dividers betwe the cubicles. 2个人坐一排，每个格子用6英尺高的办公墙分开。

Middle age is the period in life when your children leave you one by one,only to return two by two. 中年是孩子们一个一个离开你、而终归一双双回来的时期。