Using the given words to combine the two sentences into one

Using the given words to combine the two sentences into one
1 keeping the environment clean is very important(It "s)
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2 I"m very sad that wasn't accepted in that group (adj+toV)
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3 Do you know the man ? the man is talking to Tom(Ving)
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4A bridge has been declared unsafe .It was built only two years ago(V3/eD)
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