Saving the earth（The Third Period）

ss: if i had known that air conditioners cause so much pollution, i would never
 have bought one.
t: quite right. in some special forms of unreal conditional clauses, when “if” is left out, part of the predicate like had, should, were should conies before the subject. that is to say, inversion can  be used instead of “if”. are you clear about that?
ss : yes.
t: next, look at the last two sentences, to avoid repetition,“as” and “ nor” are placed at the beginning of the sentences which say that people(or thing or situation) are the same as others that have been mentioned. in this case, the structure “as/nor+ auxiliary/modal/do(does, did) + subject” should be used. besides,“neither” and “so” can be used like “nor”and “as”. is that clear?
(bb: as/so; neither/nor + aux./mod. / do( does. did) + subject )
ss: yes.
t: ok. now， let's change them into the usual  word  order  sentences. wang xia ,you try the first.
ss: it is a special sentence pattern like“ there be” structure. “exist” can only
    come after “there”.
t: yes. sit down, please. then the next sentence.
ss: china's then premier zhu rongji was among the speakers, who stressed the need for equality and fairness in the world.
t: …
s3: we will not be able to improve the situation until we know more.
s4: we can save the earth only by changing the way we live.
s5: if i had known that air conditioners cause so much pollution, i would never
    have bought one.
s6: a better understanding of the environment is necessary, and the willingness to act is necessary, too.
s7: without international cooperation, developing countries can't prosper. sustainable development will not be possible either.
step vi grammar practice
t: well, now please turn to page 70. look at the first part ,grammar: rewrite the
   following sentences, beginning  with the underlined part. first study the example, and then complete each sentence below. a few minutes later, i'll check
   your work. begin now.
suggested answers:
1. not until we stop polluting our lakes and rivers, will we have enough drinking water
2. only by learning to live in harmony with nature can we save the earth.
3. only after the meeting did 1 know that air pollution causes almost three million deaths every year.
4. only with international cooperation can sustainable development be possible.
5. not only is the earth summit a place to talk about problems, but also a place to find solutions for the future.