听音给下面的句子排序。
(    )（1） The Earth is getting hotter and hotter.
(    )（2） Why do people cut down trees?
(    )（3） People cut down trees to make more roads and buildings.
(    )（4） Farmers need the land to grow food.
(    )（5） Trees can help to make the air cool and fresh.
(    )（6） We need to plant more trees.