But we found nearly half on them were mouldy. We can't accept them anyway.
但是我们发现差不多一半发了霉。无论如何我们不能接受。
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。