用括号内所给单词的适当形式完成短文。

    What will our life be like by the year 2100? It's difficult for us ____ (imagine). People ____(live) on the earth for so many years. It is becoming more and more crowded and polluted. Maybe people will live on the other planet—Mars. Astronauts ____ (not be) to Mars yet so far. Let's imagine what our life will be like on Mars. I think life on Mars will be better than ____ (those) on earth in many ways. People will have more space. Robot will do most of work, so people will have more time for ____ (hobby). What's more, there will be no school on Mars. Every student will have a computer at home. They can study, do their homework and take exams online.