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Coal began as trees and plants．Several 1 years ago，every autumn 2 of the trees died in the forests，and more trees and plants grew．Mud and sand brought by the 3 pressed down the dead trees．

   4 years went by, new forests grew．This had happened many times．By the great pressure of the earth，the mud and sand were 5  layers(層)of rock．The 6 forests were turned into layers of coal．

  If you go to a mine，sometimes you can see lines  7 leaves．They help scientists to know what kind of trees and plants the coal was  8  。

Coal was probably first discovered in China．The first coal was found in the banks of rivers or from hillsides．People found this black Stone 8  for making fires．They began to 10 for it and the first coal mines were started．

1．A．thousand of  B．thousands    C．millions of    D．million

2．A．some    B．a(chǎn)ll    C．none   D．few

3．A．man    B．water    C．a(chǎn)nimals   D.forests

4．A．For    B .Since    C.As      D．With

5．A．become    B．turned    C．turn into    D．changed into

6．A．died    B．dying    C．dead    D．death

7．A．a(chǎn)s    B．1ike    C.of    D．with

8．A．called    B．formed    C．from   D．under

9．A．could use    B．could be used    C．can be   D．can be used

10．A．dig    B．take    C send    D. pay