Unit 20   Archaeology教案

t：very good.the second one?s:…step ⅳ  grammar(teacher shows some sentences on the screen.)t:do the sentences a and b in each pair have the same meaning?ss:yes.both of the two sentences in each pair have the same meaning.t:are there any differences?who’d like to try the first pair?s10:the subject of sentence a is an infinitive phrase,while that of sentence b is “it”.in sentence b,“it” is used in the subject position to stand for the infinitive phrase.the reason why the sentence is written like that is that we want to keep the balance of the sentence.am i right?t:yes.you’re right.sentence b is more usual in everyday english.the second pair,li ping,try please.s11:in sentence a,the subject is a that-clause,while the subject of sentence b is “it”,which is used in the subject position to stand for a clause.t:very good.the sentence structure “it is+adj.+an infinitive/a clause”is very useful in learning english.(teacher writes the sentence structure on the blackboard.)can you make a sentence with the sentence structure?s12:let me try.it is dangerous to go out alone at night.t:good.wang wei,make a sentence with the structure.s13：it is natural that a child should love its mother.(teacher writes the two sentences the students made on the blackboard.)t:well done.now.let’s do an exercise.turn to page 78 and look at ex.1 in grammar.rewrite the following sentences using “it”.five minutes later,i’ll check your answers.suggested answers:1.it is a great honour for me to be able to join in the archaeological research project.2.thanks to modern technology,it is possible to find out more facts about the man buried in the grave.3.it is still unknown whether the man organised the construction of stonehenge.4.it is a mystery how early men constructed stonehenge without the use of modern technology.t:you all did very well.now,please look at the screen.(teacher shows the following on the screen.)in this pair,sentence a and sentence b have the same meaning.sentence a includes a very useful sentence structure.do you know what it is?ss:yes.it is:it be+p.p.+that-clause.(teacher writes it on the blackboard.)t:look at the blackboard,please.here “it”is also used in the subject position to stand for a clause,but it is different from what we reviewed just now.is that so?ss:yes.t:the sentence pattern “it be+p.p.+that-clause”can often be changed into the sentence structure “people+vt.+that-clause”.the past participles used like that in the sentence structure are: reported, believed, thought, proven, known, hoped, suggested, etc.