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Because they destroy so many insects, and insects include some of the greatest enemies of the human race.

因為它們能消滅那么多的昆蟲，其中包括一些人類的大敵，

and we have to lower into the ground and haul out of the ground great lengths of drill pipe which are rotated by an engine at the top and are fitted with a cutting bit at the bottom.

我們必須把很長的鉆桿一節(jié)節(jié)地鉆入地下，然后再從地下拉出來。鉆桿頂部安裝的發(fā)動機帶動鉆桿旋轉，它的底部裝有鉆頭。

How it came about that snakes manufactured poison is a mystery.

蛇是怎樣產生毒液的，這是一個謎。

that the annual drug bill of the Health Services is mounting to astronomical figures

衛(wèi)生部門的年度藥費上升到了天文數(shù)字，

Education in the wilderness is not a matter of monetary means.

荒涼地區(qū)的教育不是錢的問題，

a wave length (the horizontal distance between two wave crests),

波長（兩個浪峰間的水平距離）