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they can locate and steer clear of obstacles -- or locate flying insects on which they feed.

并能通過回聲來確定并躲開障礙物，或找到它們賴以為生的昆蟲。

Some of the bigger firms are engaged in researches which are of such general and fundamental nature that it is a positive advantage to them not to keep them secret.

某些大公司進行的研究屬于一般和基礎性的研究。因此不保密對他們才有利。

All this was comparatively slow until, with the coming of science, the tempo was suddenly raised.

所有這些發展都比較緩慢，而隨著科學的到來，增長的速度才突然加快。

he realizes its volume, as the space that the shape displaces in the air.

他能意識到物體的體積，那就是它的形狀在空氣中所占的空間。

The administrative overheads of a business are low to the extent that everyone working in the business can be trusted to behave in a way that best promotes the interests of the firm.

如果企業中的每個人都在真誠地為提高企業利潤而工作，那么企業的管理費用就會降低到相應的程度。

Some hotels supply boiled water on request and this can be used for drinking, or for brushing teeth.

有的酒店根據要求可提供開水，這些開水可用于飲用和刷牙。