Unit 13 Were tying to save the earth.Section A 1a-1c【Im the best!】I. 选择合适的单词或短语填空，使句意完整。be full of a lot of black smoke used to do instead of play a part in close downthe bottom of clean up1. The river is very dirty. Even _ the river was full of rubbish.2. The air is badly polluted because of _.3. Everyone in the town should _ cleaning up the river.4. The government must_ the factories.5. We had better take a bus_ driving.II. 单项选择。1 You should _ if you find litter on the floor. A clean it up B clean up them C clean up D clean them up2. There were no more fish for fisherman _. A to catch B catch C catching D caught3.There _ a clean river in front of the house, but it is filled with rubbish now. A used to have B used to having C used to being D used to be4.-What can we do to cut down _?-We should take the bus or subway instead of driving. A land pollution B air pollution C noise pollution D water pollution 5.Look! The students _ rubbish in the bins. This is turning ugly places into beautiful ones. A are throwing B threw C have throwing D will throw【Challenge Myself Improve Myself】6. -Excuse me, sir. Youd better not smoke here. Look at the sign.-Sorry, I_ it just now.A havent seen B hadnt seen C didnt see D dont seeIII. 【百变小赢家】你能想出更多保护环境的措施吗？赶紧告诉自己的小伙伴们一起努力吧！请使用不同的表达句式哦！_