Cruises are becoming more and more popular, with around 20 million passengers per year now enjoying holidays on board luxury ( 奢侈的 ) ships. More people see a cruise as the perfect way to sit back and do nothing, and enjoy time off work. But what is the effect on the environment of this trend?

    Although it usually takes less energy for a vehicle to move through water than over land, cruise ships are often massive, with the biggest ones carrying up to 6,000 passengers. Moving such large vehicles requires huge engines which bum as much as 300,000 litres of fuel a day. One scientist has calculated that cruise ships create as much pollution as 5 million cars going over the same distance. Because they are out at sea, they also burn dirtier fuel that isn't allowed on land. Unfortunately, no government has control over the amount of air pollution out at sea. Cruises also produce huge amounts of rubbish, and cruise ships aren't usually good at recycling. Waste water from showers and toilets is usually poured directly into the sea - as much per day as from a small town. Waste food from restaurants isn't put into the sea, but still causes problems when brought back to the land.

    Cruise ships also cause difficulties in the cities where they stop. Popular destinations can get five or six ships per day, with thousands of tourists at a time. Good for restaurants? No. Restaurant owners complain that the visitors look around for a few hours and then return to their ship to eat. What's more, the crowds can put off other tourists, who complain that the streets are too busy.

    Some towns have banned (禁止) cruise ships or put a limit on the number that can stop at the same time. People who care about the environment worry that as the cruise industry continues to grow, so will the issues for our planet.

    Sometimes people cry when they are sad. Other times people cry tears of joy. But your eyes make tears all the time, whether you are crying or not. Do you know the tears help keep your eyes healthy? They keep your eyes from drying out. A special area of the eye drips (滴) all the time. It keeps the eye humid.

    If you look in a mirror, you can see tiny holes in the comers of your eyes. Each hole leads to a small tube that runs to your nose. Tears run slowly into this tube drip by drip. Day and night the holes drain (流走) the tears away. If they didn't, you would always look as if you were crying.

    If you begin to cry, there are many more tears. The holes can't drain all of them. Then extra tears run out onto your face.    

    Tears help keep eyes safe. If there is something harmful in the air, the eyes fill with tears. These tears coat your eyes. They keep the harmful air out.

    Contact lenses(隐形眼镜) can make the eyes too dry. Some people have to add tears to their eyes. They buy bottles of eye drops to keep their eyes wet.

    Uber (优步)announced that it plans to invest 20 million in developing an aircraft in France over the next five years.

    It will open a new research and development center in Paris﹣its first technology hub outside of North America.

    "France is a perfect home for our next step forward with its strong history of research and development, world class engineers and a unique role in aviation (航空)worldwide,"Uber said in a statement.

    Uber already has R & D offices in Pittsburgh, Toronto, and San Francisco. They focus mainly on Uber's self﹣driving technology, but have also been working on Uber's Elevate flying car program.

    The Advanced Technologies Center in Paris will open later this year and only focus on flying cars. It will conduct research into airspace management, real﹣time communication networks, energy storage, and charging systems.

    Uber's announcement, made at a tech meeting in Paris, has been supported by French President Emanuel Macron, whose ambitious economic reforms are to attract more foreign investment.

    The company also announced a five-year research partnership with Ecole Polytechnique, a leading French institute of technology.

    Uber has been working on its flying car program since 2016. NASA became a partner for the program a year later by developing air traffic management for a fleet of flying cars.

    Uber expects flight to become a daily part of our transportation lives. The company believes it can offer rides in flying cars for about the same price as an Uber X ride. This technology may completely change our transportation lives in the future.

    Learning dances sounds interesting. But if you really want to become a dancer, read1following guide for new dancers.

    If you want to become a dancer, you should first2a dance style. There are some skills in each kind of dance. And we need to practise3a lot. And knowing which dance style you just want to learn can help you practise harder.

    Find a dance class. When you have decided4dance classes, it is important to choose your dance teacher 5. It is easy to get into some bad habits, and you may find it hard to correct (改正) them later on. And what is the6is to choose a teacher and you really love his or her dance style.

    Different styles of dance clothing are7for different styles of dances.

    8example, we need special dance shoes for most dance styles. And your dance teacher will probably have some requirements on other things. Ask him or her for more about9to wear.

    Besides, the floors of dance classrooms should be soft,10you may be injured when you dance on hard floors.

Robots are very important in our daily life now. People like robots because they can do things for us. They can do housework. They can deal with data (处理数据) fast. Some people think robots can do everything nicely. But some things that are easy for us are difficult for robots. For example, robots have difficulty picking up things. This may make you feel surprised because even babies can pick up things easily. That's because our brains tell us how to use our hands to hold things. But robots can't understand these kinds of things. So they often break or drop things. 

Many scientists are trying to deal with this problem. Among them is Ken Goldberg from the University of California, Berkeley, the US. He has studied the problem for years. Finally, he came up with an answer to the question. He built a database for robots. All kinds of information about a thing, such as its size and shape, are in the database. Before a robot picks up a thing, it can find the information about the thing. In this way, the robot can pick up the thing easily.