With the development of the Internet, many people use it very often, including some teenagers. But many parents are worried about that their children may meet with something unhealthy online. To solve this problem, a new search engine for children named Kiddle has appeared.

     Search results are filtered, so only safe website are shown and descriptions are written in simple language. Searches with bad words are shut off, too. Kiddles uses the same color as Google in its logo and a similar design on its homepage, too— with an extra robot picture. The top three Kiddle research show safe websites and pages written specially for kids and those websites and pages are well chosen and checked by Kiddle developers. The fourth to seventh results will be safe and trusted websites that are not written for adults. They provide expert content, but are harder for kids to understand.

     Unlike on Google, most results appear along with large thumbnail pictures(缩略图) to make it easier for children to find what they are looking for. For example, when you search for “meow meow”. Google produces pages for information about a drug(毒品)，but Kiddle lists information only about cats. The company explained, “Websites which appear in Kiddle search results satisfy family–friendly requirements, as we filter websites with unhealthy content.”

    Have you ever wondered why birds sing? Maybe you thought that they were just happy. After all, you probably sing or whistle when you are happy.

    Some scientists believe that birds do sing some of the time just because they are happy. However, they sing most of the time for a very different reason. Their singing is actually a warning to other birds to stay out of their territory.

    Do you know what a 'territory' is? A territory is an area that an animal, usually the male, claims as its own. Only he and his family are welcome there. No other families of the same species are welcome. Your yard and house are your territory where only your family and friends are welcome. If a stranger should enter your territory and threaten you, you might shout. Probably this would be enough to frighten him away.

    If so, you have actually scared the stranger away without having to fight him. A bird does the same thing. But he expects an outsider almost any time, especially at nesting（筑巢）season. So he is screaming all the time, whether he can see an outsider or not. This screaming is what we call a bird's song, and it is usually enough to keep an outsider away.

    Birds sing loudest in the spring when they are trying to attract a mate and warn others not to enter the territory of theirs.

    You can see that birds have a language of their own. Most of it has to do with attracting mates and setting up territories.

    Most people agree that trees look nice, but not everyone knows that trees can also help cities save money. A few years ago, the US Forest Service studied trees in Chicago. They found that just one tree can save a city hundreds of dollars over its lifetime.

    Trees can save money by helping people save energy(能源). Trees stop the sun shining on buildings. They also block(挡住) the winter wind. That helps people use less energy to make their homes or offices warm or cool. Saving energy is saving money.

    Trees have another way to help a city save money. When it rains, there will be a lot of water in a city's sewers (下水道). Cities need lots of money to clean that water. But before the rainwater gets to the dirty sewers, trees can take some into themselves. With the help of trees, there is less water to clean.