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Trees are among the biggest and longest-living things on Earth, some dating back longer than the oldest buildings. But (1)_______ being nice to look at, trees also play an important role in improving the quality of our lives. On a world-wide (2)_______, forests help to slow down the effects of global warming by using up the gas known as carbon dioxide and giving (3)_______  the oxygen we need to breathe. At local neighborhood level, trees also (4)_______  important environment benefits. They offer shade and shelter, which in (5)_______  reduces the amount of energy needed to heat and cool nearby buildings; at the same time, they also remove other impurities from the air we breathe.

Điền vào số 3