What is a museum? A museum is a good place to keep old and beautiful things. A museum may be a place to learn about science and a place to find out about art or people or animals.

    What is inside a museum? Some museums have old cars and airplanes. Many museums have pictures and statues(雕塑). Others have rocks and old bones (骨头). One museum even has a real old street inside. It has shops and people's statues doing business. It looks so real that one might feel that he was back to the old time.

    Many cities have museums. Some very small towns have museums, too. Indianapolis has a children's museum. Children do not have to pay (付款) to get in. Children often go to the museum. They like to look at the dinosaur (恐龙)bones. They see a white bear ten feet tall.

    On Saturdays, Indianapolis children can hear talks about animals and trees. They see movies. They take hikes. They even learn to make things there.

    In many high schools, there are strict rules about using mobile phones. If your phone rings in class, for example, the teacher will be very angry.

    Every mobile phone has a ringtone (铃声). It tells you that someone is calling you. Now, there is a ringtone called “mosquitotone (蚊子铃声)”.

    Mosquitotone has a special sound. Only children and teenagers can hear it. As we get older, we are unable to hear some sounds with high frequencies (频率). As a result, a child or teenager can hear the mosquitotone ringtone, but someone of 20 or older can't.

    But sometimes, people over 20 can hear the ringtone. One British student's phone uses mosquitotone. In class, the student's phone rang. The 22-year-old teacher looked at the student and became unhappy. “I heard that. You know the rule：no mobile phone in class. ”

    Not all the students are interested in mosquitotone. Jerry Jones, a high school student of 17, says, “Using mosquitotone too often is bad for our hearing. I may use it for pleasure, but not in class. It's unfair(不公平的) to the teachers！”

    What do parents think of mosquitotone？“I think it is perfect for places like movie theaters,” says Connie Neeson, 44. “Think about it. You're watching a film and someone's mobile phone rings. Mosquitotone is good because many people don't hear it. However, it also has a bad influence（影响） on their study if students use it in class. ”

    The world is not hungry, but it is thirsty. It seems strange that nearly 3/4 of the Earth is covered with water while we say we are short of（短缺）water. Why? Because about 97% of water on the Earth is sea water which we can't drink or use for watering plants directly(直接地）. Man can only drink and use the 3%-the water that comes from rivers and lakes. And we can't even use all of that, because some of it has been polluted(污染）.

    Now more water is needed. The problem is Can we avoid（避免）a serious water shortage later on? First, we should all learn how to save water. Secondly, we should find out the ways to reuse it. Scientists have always been researching in the field. Today, in most large cities water is used only once and then runs to the seas or rivers. But it can be used again. Even if(即使）every large city reused its water, there would not be enough. What can people turn to next?

    The seas seem to have the best answer. There is a lot of water in the seas. All that needs to be done is get the salt out of the sea water. This is expensive, but it's already used in many parts of the world. Scientists are trying to find a cheaper way of doing it. So you see, if we can find a way out, we'll be in no danger of drying up.

    Is it a bird? Is it a plane? No, it's your online shopping! Imagine a world where your shopping was dropped off on your doorstep by a delivery (投递) drone (无人机). Well, many companies are working to make this idea a reality. Among them, Amazon and UPS are just some of the front runners in the race to have the first ever business drone delivery service.

Pros:

    ①Fast. Delivery drones can cut down the time of delivery to just 30 minutes.

    ②Environmentally friendly. Companies like UPS have started that the use of drones would cut down on waste gas (气体).

    ③Cheap. Though exact prices for drone delivery aren't known, companies such as Amazon suggest deliveries could be as cheap as $1.

    ④Emergencies. Drones can fly straight to areas they're needed without using any roads.

From Dispatch (分派) to Doorstep:

    Usually products available for drone delivery will be stored somewhere nearby. Customers will choose these products through shopping apps or websites. The suggested weight to be carried is no more than 2.3 kilograms. Once the products are put into the drone, it will take off from the dispatch center. It will fly below 120m and avoid any "No Fly Zones" like airports for safety reasons. Before landing, a pad will be placed in the customer's garden for the drone's landing. After the drone puts down its product, it will rise to return to the dispatch center. So a drone delivery could one day be just a touch of an app with your finger.

Cons:

    ①Weather like strong winds, lightning storms and heavy rainfall may influence deliveries.

    ②Dispatch centers will have to be built within certain distance.

    ③Drones might be unable to land safely in high-rise buildings.

    ④Something will have to be done to make sure about the safety of the products and of people walking below.

    The future of flying transportation

    Though the delivery drone service is alive with new technology, we are a long way from seeing them through the air. There are still many difficulties such as flight law making. It's said that by 2021 we might see the beginning of drone delivery systems in action.

    Can you imagine a pair of shoes that could tie themselves? All you have to do is put them on and push a button. Well, this idea is becoming a reality. The shoe company Nike created the self-tying shoe! This idea first came from the film Back to the Future II, Nike has been working for years to create a shoe that can do this in real life. They have finally done it with Nike HyperAdapt 1.0.

    So how does it work? According to Nike, the shoe is “powered by an underfoot-lacing mechanism(脚下系带装置) small motor that has the power to lace the shoes, All you have to do is put them on, and at first, the shoes are very loose(松的). But then you can push the "+" perfect fit for you. To take them off, all you have to do is push the "-" button, and the shoes will be easily off.

    They haven't been widely released to the public yet, and the price of the shoes is quite high.