What we saw and what we heard/ What we experienced during the Spring Festival made us deeply understand/ fully aware that millions of ordinary people are the greatest and that happiness is achieved through hard work.
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16.答案：So quickly is artificial intelligence changing the whole world that it is hard for you to predict what life will be like in the future.
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17.答案：It’s no use complaining about too much homework, you may as well learn how to manage your time properly.
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18.答案：Whether it is a waste of resource for a college student to be a security guard after he graduates from college is the topic of the debate that I hosted yesterday.
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19.答案：In recent years, the idea that electronic whiteboard system should be applied to classroom teaching efficiently and flexibly has been widely accepted, hasn’t it? (同位语从句可以后移;副词也可提前)
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20.答案：We firmly believe a more hannonious society will be built people will live and workhappily and they will besatisfied with their life physically and mentally. 解析：