9.The earth was just a cloud of (71)dustafter the"Big Bang".The earth (72)explodedloudly with fire and rock.They were in (73)timeto produce many things,which were to make the earth's atmosphere.As the earth cooled down,water began to appear on its surface.It allowed the earth to dissolve (74)harmfulgases.Then life began to develop.
The first small plants (75)multipliedand filled the oceans and seas with oxygen.This encouraged the (76)developmentof early shellfish and fish.Land animals such as insects,reptiles and dinosaurs and so on appeared after green plants appeared.Small clever animals (77)spreadall over the earth.They are putting too (78)muchcarbon dioxide into the atmosphere,which (79)preventsheat from escaping the earth into space.Whether life will continue on the earth for millions of years to come will (80)dependon whether this problem can be solved.