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complete the sentences using conditional 2 and 3
1. If people hadn"t polluted the planet, many species of animals __ (not disappear)
2. If countries __ (spend) more money on scientific research, scientist would have solved some environmental problems
3. If people had dreamed more about space flight, they __ (find) another planet to live on
4. If people __ (use) bicycles more, the air would be much cleaner
5. If I had met Tsar Ivan, I __ (ask) him not to kill his son