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Choose the best words or expressions and complete the passage (选择最恰当的单词或词语完成短文)
______________years ago, people in London got water from a river. But later the river became very____________because many factories were built near the river. People threw many things____________the river. By the year 1830, the city was polluted. No fish could live in the water. And nobody could__________the water. People tried their best____________it. In 1960 the river became clean____________, and in 1990, 78 different kinds of fishes were found in it.

1．	A．Hundred B．Hundreds of C．Hundred of D．Two hundreds of

2．	A．clean B．dirty C．beautiful D．wide

3．	A．on B．at C．over D．into

4．	A．drink B．eat C．pollute D．make

5．	A．change B．changed C．to change D．changing

6．	A．too B．again C．so D．late