1. And we have only to turn to that extraordinary discovery of echo-location in bats to see a case in which the voice plays a strictly utilitarian role.
    我们只要看一看蝙蝠回声定位这一极不寻常的发现，就可以探究一下声音在什么情况下有绝对的实用价值。

2. Extraordinary discovery of echo-location in bats to see a case in which the vioce plays a strictly utilitarian role.
    我们只要从蝙蝠的回声定位这一项非凡的发明中, 就能看到声音起的纯粹实用作用的例子.