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 Period 2AThink and say  略BListen and match1The smoke from factories makes the air dirty.2We can ride bikes to keep the streets clean.3There is a lot of rubbish in the river. The fish are dead.4We can plant more trees. Trees can help keep the air clean.(1 b2 a3 d4 c)CRead and complete  1 makes2 keep, take3 move4 factorie   | 
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