—I'm sorry. I was having dinner with my friends___________ you were looking for me.

    Would you like to live in a city where buildings turn the lights off for you, and self-driving cars will find the nearest parking space themselves? Although it might sound a little far from you, living in a "smart" city like this could happen sooner than you think.

    Great changes have taken place in towns that we have lived in for centuries, while completely new cities are being built. One such place is the city of Songdo. Every home there will have a "telepresence" system (远程监控系统)—allowing users to control the heating and locks, take part in video meetings, and receive education, health care and government services. Around the city, escalators (自动扶梯) will only move when someone is on them, and offices and schools will all be connected to the system.

    The great mind behind Songdo is from the company Cisco. In fact, technology companies around the world such as IBM, Siemens and Microsoft are already in the business.

    About 75% of the world's population will live in cities by 2050, so cities will need to be more modern to deal with the coming problems. "Making cities smarter is one way out, and I think this will in turn make cities greener," said Dan Hill, head of a research company.

—Sorry, I didn't hear it. I ___________with my dog.

    How cool would it be if people could（travel）in tubes（管道）? They may travel to another city in just（minute）. In the near future, this might not only happen in films,also in real life. The first open air test of the tube train took placeMay 11, 2016. It happened in the Nevada desert, the USA. Elon Musk（have）the idea of developing the tube train. He isfounder（创始人）of the American space company SpaceX. He calls the tube train the Hyperloop. The Hyperloop will be even（fast）than planes. It will go about 1, 200 kilometres per hour. Planes usually（flight）800 to 1,100 kilometres per hour. The company Hyperloop One is still（work）on the tube train. They want people to travel（use）the Hyperloop by 2021.