根据上下文提示,填写正确的单词补全短文。

I think life in the future is quite different from now. For example, 20 years, people won't use paper money anymore, because  will be free. As for education, kids won't go to school. They will study at  on computers. Every family will have robots. They'll talk  people and make them happy. They also help people do all housework. Thanks to the robots, people will have more free time, so families will  time staying together every day. The life in the future won't be the  as it is today. To protect our world, we should use  fresh water, and we need to  more trees. I believe the future world will be a  place to live in.