21.Instead，they tend to be endlessly recycled in the food chains
1）tend to do/be：be likely to do/ be 趋向……。往往……
eg：Prices are tending upward.物价趋于上涨。
In primary and secondary schools girls tend to work harder than boys.在
小学和中学时，女孩比男孩用功。
2）be recycled ：使再循环；回收利用；重心利用
The recycled water is used to water plants.
再循环的水被用来浇灌植物。
3）food chain：食物链
4）be dependent on：依赖于
It is not good for students to be too dependent on their teachers
学生过于依赖于他们的老师不太好。
22.One might guess that this time Carson the reader might have reminded Carson the scientist of some passage in Shakespeare's most famous play.
remind sb of sth：make sb.think of sth.使人想起，提醒。
eg：Please remind me of getting up at 5 tomorrow morning.
请提醒我明天早上5点起床。
The picture reminded me of my childhood in the village.
那张照片使我想起我在那个村庄度过的童年。
23.Prince Hamlet used revoltingly grisly images in the vicious baiting of his hatred uncle when he told him that in nature's food chain，the worm is king.
哈姆雷特王子使用了令人作呕的形象比喻来设下恨毒的圈套，引他那个可憎的叔父上钩。他对他叔父说，在大自然的食物链中，以蛆为王。
24.Rachel Carson know of this poisonous cycle.
know of：知道……的存在；听说 be aware of the existence of，hear about
eg：Do you know of any filling station around here？ 你知道这一带有加油站吗？
I don't know the writer，but I know of him.我不认识这个作家，但我听说过他。
25 And she knew now，as her own observations were confirmed by fellow scientists all over the country，that this “worm” now carried a heavy concentration
1）as 引出的是原因状语从句
confirm：确认，进一步证实
This view is confirmed by the fact that…这种观点以被…事实所证实。
approve：同意、批准、赞成
The plan was approved by the Ministry of Communication.
这个计划得到了信息部的批准。
2）concentration （concentrate）：集中、专心 指把人或物集中在一起，把精神，注意力集中在某一事物
Chess requires great concentration.下棋需要全神贯注。
focus：焦点、中心
The government put the revival of economy as the focus of its work.
政府把振兴经济作为它的工作重点。
26.It could be passed on to fish，to other animals，to their food supply and to men and women and children throughout the earth.
pass on （from…） to…：（及物） 把……（从……）传给；（不及物）（从……）转移到……
We hope Sino-Japanese friendship will pass on from generation to generation.
我们希望中日友谊将世世代代继承下去。
The money passed on from one to another until it reached the conductor's hands.
钱由一个人传递给另一个人，一直递到售票员的手里。
27.In spite of fierce opposition from the chemical industry，from powerful government agencies，and from
