China successfully ____________ a man-made satellite in 1970, which was a breakthrough in Chinese aviation history. 2. Many college students who have ________________ English for more than ten years can’t speak fluently in English. 3. ____________ tribes lived by fishing, hunting and gathering, and they hunted wild animals with crude stone implements. 4. He ____________________ the anti-nuclear movement after the nuclear leak accident. 5. Cycling is the use of bicycles for transport, recreation, or for sports. People engaged in cycling are referred to as“____________”. 6. Barter trade prevailed at the time of famine. One can ___________ a loaf of bread ___________ a coat. 7. This conference aims to tackle the problems and ____________ strategies to help nations adapt to climate change. 8. More often than not, teenagers who ____________ school have trouble in finding high-salary jobs. 9. Buddy Holly was killed in a plane ____________ while on a singing tour in the Midwest. 10. These days, if a job is available, young people often have to ____________ more experienced workers