A Cloud of Hope and Danger

    In 2050, a small cloud floats through the air in a hospital operating room(手术室). In the room a patient, suffering from cancer, lies on a table. The cloud surrounds (包围) the patient, her body and filling her lungs (肺). The cloud is not smoke or steam. It is made of millions of microscopic robots called nano-robots(纳米机器人). These tiny robots move from cell(细胞) to cell in the body, destroying the cancer cells.

    Fighting cancer with nano-robots is only an idea today, scientists say that it would be possible in the future. Using nano-robots for good purposes such as fighting disease or repairing the environment may be the to many of today's problems.

    However, nano-robots could be a risk as well. Since nano-robots are so tiny, they will have to work in large teams of many thousands to 'many millions. For this reason, nano robots will have to be programmed to build . Scientists will not have the ability to build millions of nano-robots one by one.

    This to reproduce(复制)is making some scientists worried. What if something goes wrong in the programming? Quite a lot of crazy nan-orobots would be far than any disease. Some people think that if they get out of control, nan-orobots could destroy the Earth.

    What should be done? Should we continuenan-orobots or should we search for other methods? This is one of the many difficult that we have to make in the future.

When the other models appeared on the stage, the audience cheered and clapped. Then it was Niu's turn. The audience suddenly became . However, after four or five seconds, Niu heard someone next to the stage say in admiration, "So cool!"

Niu Yu, 24, became a(n) star at Shanghai Fashion Week for her confidence, even though she was wearing a prosthetic leg. When Niu was only 11, she lost her right leg during the Wenchuan Earthquake.

Niu has won lots of praise. This gives those who have prejudice(偏见)against the disabled a hit on the nose. "I by something they said. They said the traditional view was that sports were for people with legs, but sports should be a kind of spirit. Even though I have lost a leg, I still deeply love sports and will do so forever, " Niu said. Actually, Niu first drew the public's attention when she a marathon — a 42-kilometer race in 2018, which was held in Wenchuan to mark the anniversary （周年纪念）of the earthquake.

Now, Niu works as a photographer and has more than 850,000 on social platforms, such as Douyin. "I feel I have a social responsibility to bridge the disabled and the public. Showing my life to the public can allow them to understand our group and can also tell other disabled people that our society is more tolerant（宽容）than they imagined, " she explained.

Laughter is good for you, and that's no joke! A good laugh helps you right away. When you laugh, changes in your body. For example, you take in  air than usual, which is good for your heart. A good laugh increases your heart rate. When you laugh, your brain also releases (释放) chemicals that make you feel happy. Laughing can also make you feel relaxed for up to 45 minutes.

Laughter can  reduce pain. You probably don't want to chuckle (偷笑) when you're hurt, but laughter helps the body make its own  medicine. Laughing is also great exercise! Research  that laughing 100 times is as good as riding a bike for 15 minutes.

So why don't you try laughing out loud every day?