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In the past, the man didn’t have to think about the protection

76. _________

of his environment. There used to be many people on earth，

77. _________ 

but natural material resources seemed to be unlimited.  

78. ___      

Today things are different . The world become too crowded.   

79. _________ 

We are use our natural materials too quickly. At the same time,

80. _________

we keep polluting our environment from dangerous chemicals.  

81. ________

Dustbins are filled up with cans and bottles that once holds

82. ________

beer, coffee or Coca-Cola. Everywhere peoples are always

83. ________

throwing away wrappings from food or clothes and all kinds

84. ________

of unwanted things, some of things are difficult to get rid of.

85. ________