【正文】 them?Estuaries absorb nutrients and pollutants from water ing from inland sources, thus cleaning our water.4. Why are estuaries more sensitive to pollution than other areas?Since estuaries act as filters, many pollutants end up in the estuaries.5. Why are estuaries important to human beings?Estuaries are important to human beings because we like to study and relax in them and because they contribute to the economy. III. Summary the main idea of each paragraph explains what an estuary is and describes some of its characteristics. explains why estuaries are such good “nurseries”. describes the “filter function” of estuaries and notes that estuaries are sensitive to pollution and should be protected. explains there are also recreational and economic reasons for protecting our estuaries.IV. Language pointsUseful expressions:2. the source of life on earth3. A river meets the ocean.4. create a unique environment5. nature’s young ones6. enjoy all the benefits of7. face many of the dangers8. provide energy for the ecosystems9. absorb nutrients and pollutants10. inland sources11. make estuaries very sensitive12. be sensitive to13. recreation and education for human beings14. have fun15. on the beach16. have endless opportunities to do17. study life in the habitat18. a variety of19. contribute to the economyImportant sentences:1. Finally, estuaries provide both recreation and education for human beings.（1）供給 That hotel provides good meals.（2）約定；規(guī)定 The law provides that valuable ancient buildings must be preserved by the government.（3）provide for ＝support 支持；供養(yǎng) He has a wife and five children to provide for.（4）provided that 假使，在……條件下 I will go , provided that you go too.2. The diversity of life in estuaries is incredible birds, fish, marine mammals, shellfish and other species all e here to live, feed and reproduce.Incredible adj. 難以置信的，不可思議的The film star has an incredible car in addition to a large house.這個電影明星除了一幢很大的住宅外還有一輛極好的汽車。Incredible in不+credible 可信的3. Estuaries also contribute to the economy through tourism and fishing.through prep.(1) 通過，經(jīng)過We walked through the market to the truck park. 我們穿過市場到了卡車停車場。(2) 藉著；以…；經(jīng)由He became rich through hard work. 他靠努力工作而致富。(3) 由于；因?yàn)镸istakes made through carelessness. 由于粗心大意而造成的錯誤(4) 從頭到尾，由始至終。 在…一帶；在…之內(nèi)We traveled through France and Belgium on our holidays.我們假期里是在法國、比利時一帶旅行的。(5) 結(jié)束；完成；成功We are through school at five o39。clock. 我們五點(diǎn)上完了課。adv.(1) 穿過，通過；貫穿They wouldn39。t let us through. 他們沒讓我們過去。(2) 全程地；直達(dá)地The train goes through to Shanghai. 這列火車直達(dá)上海。(3) 自始至終，從頭到尾Have you read the letter through? 你看完信了嗎？(4) 情況好；取得成功I got through with good marks. 我考的成績很好。(5) 打通，接通（電話）Can you put me through to Mr Jones? 請幫我接通瓊斯先生的電話。(6) 透；徹底be wet through 渾身濕透V. HomeworkIII. Homework必做作業(yè)： 見作業(yè)紙選做作業(yè)： 倍速Step Four: Homework TThe Fifth Period ( The Fourth Pehe Fifth Period (GrammarTeaching Aims: 1. Review the new words appearing in the last periods2. Learn to use the rules of Modal Verbs Important Points: 1. Master the general rules2. Understand the special usage of Modal Verbs Difficult Points: 1. Use it correctly in certain sentences2. Understand the meaning of Modal Verbs in special situationsTeaching Aids 1. the multimedia2. the blackboardTeaching Procedures:I. RevisionII. Grammar Modal Verbs一. 概述情態(tài)動詞（Model Verbs）又稱為情態(tài)助動詞（Model Auxiliaries），主要有can, may, must, could, might, shall , should, will, would, ought to, need, dare等。情態(tài)動詞與其他動詞連用表示說話人的語氣。情態(tài)動詞可表達(dá)建議、要求、可能和意愿等。情態(tài)動詞沒有人稱和數(shù)的變化。（1）情態(tài)動詞+動詞完成式：must have done （2）情態(tài)動詞+動詞進(jìn)行式：must be doing （3）情態(tài)動詞+動詞完成進(jìn)行式：must have been doing （4）某些情態(tài)動詞的特殊用法：need二．具體內(nèi)容（一）情態(tài)動詞+動詞完成式情態(tài)動詞+動詞完成式即“情態(tài)動詞+ have + done分詞”，表示對過去行為或動作進(jìn)行推測、評論或判斷。1. must have donemust have done 表示對過去某事的肯定猜測。其否定或疑問形式都用can（could）來表示。例如：Since the road is wet, it must have rained last night.He can’t have missed the way. I drew him a map.“The dictionary has disappeared. Who could have taken it?”當(dāng)然對現(xiàn)在發(fā)生或?qū)戆l(fā)生的事情，要用must do 表示猜測，否定為can’t do。He must understand that we mean business.You must be hungry after a long walk.2. may / might have donemay / might have done 表示推測過去某事“也許” 比 might 表示的可能性在說話人看來稍大些。例如：I can’t find my keys. I may / might have left them at the school yesterday.3. could have done 在肯定句型中，往往用作委婉的批評。本應(yīng)該做什么。而沒做；有時也用作猜測。You could have told us earlier.Tom could have taken the dictionary.4. ought to / should have done和 ought not to / shouldn’t have doneought to / should have done 和 ought not to / shouldn’t have done 用于對已發(fā)生的情況表示“責(zé)備”、“不滿”，分別表示“本應(yīng)該…”和“本不應(yīng)該…”。例如：（1）With all the work finished, I should have gone to the party last night.（2）You ought not to have made fun of him. He is not the one you laugh at but learn from.5. needn’t have done needn’t have done 表示過去做了某事，但沒有做的必要， 意為“本沒必要…”。例如：You needn’t have waken me up 。 I don’t have to go to work today.注：表示推測過去某動作發(fā)生的可能性時，就表示的可能性程度而言，must最大，could其次，may更次之，might最小。例如：“I wonder how Tom knew about your past.” “He must / could / may / might have heard of it from Mary.”（二）情態(tài)動詞+動詞進(jìn)行式情態(tài)動詞+行為動詞進(jìn)行式（即情態(tài)動詞+ be + doing形式），表示推測或評論某動作現(xiàn)在是否正在進(jìn)行。例如：（1）He must be playing basketball in the room.（2）She may be staying at home.（三）情態(tài)動詞+動詞完成進(jìn)行式情態(tài)動詞+行為動詞完成進(jìn)行式（即情態(tài)動詞+ have been + ving 形式），表示推測或評論過去某動作是否正在進(jìn)行或