Global warming Period 3 Grammar—the Use of “It”(2)
suggested answers：
1.it_was a scientist called charles keeling，who made accurate measurements of the amount of carbon dioxide in the atmosphere from 1957 to 1997.
2....it_is the burning of more and more fossil fuels that has resulted in this increase in carbon dioxide.
step 3 grammar learning
ask the students to study the following sentences and try to summarize the structure of the emphasized sentences.
tom found my pen in the classroom yesterday.it was tom who/that found my pen in the classroom yesterday.it was my pen that tom found in the classroom yesterday.it was in the classroom that tom found my pen yesterday.it was yesterday that tom found my pen in the classroom.
step 4 summing up
try to help the students draw the following conclusions.
1.the main structure of the emphasized sentences is “it is/was...that/who...”.
2.the emphasized sentences can be used to emphasize the subject，object and adverbial(including adverbial of time and adverbial of place).
3.when we want to emphasize the subject，object and adverbial，we only need to put these parts between “it is/was” and “that/who”，the rest part shouldn't be changed.
4.when the emphasized part is a person we can use both the structure “it is/was...that...” and the structure “it is/was...who...”.when the emphasized part is not a person we can only use the structure “it is/was...that...”.
step 5 grammar practice
ask students to do the following exercises：
1.change the following sentences into emphasized sentences.(to emphasize the underlined parts.)
(1)peter lent us the money.
(2)they want money.
(3)all this happened on_monday.
(4)i didn't hear from her until_last_summer.
(5)why does everyone think i am narrow－minded?
suggested answers：
(1)it was peter who lent us the money.
(2)it is money that they want.
(3)it was on monday that all this happened.
(4)it was not until last summer that i heard from her.
(5)why is it that everyone thinks i am narrow－minded?
the last two may be a little difficult for the students.help them to get the correct answer.
2.do exercise 2 in discovering useful structures on page 29.
3.do the exercises in using structures on page 64.
first ask students to do the exercises individually，and then let them discuss and check their answers with their partners，and finally give them correct answers and deal with any problems they might meet.
step 6 getting more about the grammar
show the following sentences to the students and ask them to find what the similarity of these sentences is.