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   Trees are our friends. ______ are useful. They give ______ wood so we can ______ paper, desks and chairs. Many trees give us fruit. We all like ______ fruit. It ______ us healthy. Trees can reduce the noise. It can also keep water and soil. Our city looks beautiful ______ trees. Trees also help keep the air ______. Trees are important (重要的). We ______ cut down too ______ trees. We should protect trees and plant ______ trees.