分类：教育/科学-外语学习
问题：6Blivecutbedosave1.Wemust_____th 
live    cut     be     do     save1.We must_____the Earth.2.I_____ in Shanghai for more than 20 years.3.There______air and water on the Earth.4.The people ______down the forests. They must stop______this.
回答：1.We must___save__the Earth. 
2.I___live__ in Shanghai for more than 20 years. 
3.There___are___air and water on the Earth. 
4.Those people __are_cutting___down the forests. They must stop___doing___this.