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课时提升作业(十一) 必修4 Unit 2 (建议用时25分钟) . 单项填空 1. (2017·长沙模拟)Where is Flight MH370? Investigators ________ to answer this question for several months. A. were attemptingB. have been attempting C. are attempting D. will be attempting 【解析】选B。句意: MH370航班在哪儿呢? 几个多月以来调查人员一直试图回答这个问题。“试图回答这个问题”发生在过去, 并且一直在进行, 故用现在完成进行时。 2. The charity sale our school organizes every year has taught us much. ________ we would never have learned it in class. A. Therefore B. Meanwhile C. Otherwise D. Instead 【解析】选C。句意: 每年我们学校组织的慈善义卖教给我们许多东西。否则的话, 在课堂上我们永远不会学到这些。otherwise否则; therefore因此; meanwhile与此同时; instead代替。 【加固训练】 (2017·南京模拟)The conservation area is very important for preserving many animals and plants, which would ________ run the risk of becoming extinct. A. otherwise B. therefore C. though D. instead 【解析】选A。句意: 自然保护区对保护许多动植物很重要, 不然, 这些动植物有濒临灭绝的危险。otherwise否则; therefore因此; though尽管; instead代替。 | 
