Homeless people face a lot of challenges, - such as not having enough to eat and no job opportunities. Some of the most basic challenges, - however, -are not having clean water and toiletries (卫生用品)-a big problem for homeless teens. That encouraged a young researcher to invent a multi-purpose product to help these teens.

    "I was born into a life of volunteering," said 13-year-old Leia Gluckman. And that's true. Her mom is a president of an organization providing help for homeless teens. Leia and her brother have volunteered there for years. When she was a young girl, Leia helped serve food where teens were eating. Now she's a teenager herself, and she's managing the toiletry and clothing work there.

    From her work at the center, Leia noticed that teens asked for some toiletries more than others. What they needed most often were toothpaste, body powder (粉)and shampoo(洗发水).Leia wondered whether she could create a product to serve all three purposes.

    It would need to take away dirt and oil from skin and hair. It would need to clean teeth. Also, it would need to kill bacteria (病菌)without being harmful to people. She wanted her ingredients (产品成分)to be natural, to be able to break down easily and to taste and smell pleasant. Moreover, this product had to be low﹣cost and have a long shelf life.

    Leia started by going to stores and looking at the ingredient lists for toiletries. Then she tried eight different ways. She tested each way to see how well it worked.

    Not all of them worked well. But she finally decided on three. Each includes salt and baking powder. Salt helps clean teeth and skin; baking powder helps take in bad smells. She also has some other recipes which include some special materials that give her products different tastes and smells, which would let teens choose a product based on personal preferences.

    It wasn't easy, but Leia came up with some model products. She presented them at the finals of Broadcom MASTERS science competition.

    Leia wants to develop her products further. "Could it possibly be used to drive away mosquitoes (蚊子)?" she wonders.

    "Science offers a way to go about solving problems and helping people," says Leia. And she thinks her products could benefit a great number of people, not just the homeless. Anyone in an area with little or no chance to get clean water could find her products useful, maybe refugees (难民) and soldiers who are sent to places without running water.

    Jackson was excited！He and his family were on their way to the White House, Jackson could not wait to see the President's official residence. He had been reading all about it so that he might recognize some things he saw. After standing in a long line, Jackson, his sister, and their parents were allowed to enter the 132-room, six-floor mansion. They entered through the East Wing. Jackson knew that he and his family were only four of the 6, 000 people who would visit this incredible house that day.

    The first room they were shown by the guide was the State Dining Room. Jackson learned that 140 dinner guests could cat there at one time. "What a great place for a huge birthday party！"Jackson thought.

    The Red Room was shown next. Red stain(绸缎)adorned its walls. The third room the visitors entered was the Blue Room. This room serves as the main reception room for the President's guests. Jackson wondered when the President would be out to greet him. After all, he was a guest, too.

    The Green Room was the fourth room on the tour. Jackson and his family were not surprised to find green silk covering the walls in this room.

    The last room was the biggest room in the White House. It is called the East Room. Here guests are entertained after formal dinners. Jackson wondered if they could vary the entertainment by rolling in huge movie screens so they could all watch the latest movies. He wondered if kids were invited sometimes; maybe they had huge, bouncy boxes you could jump in. Perhaps they even set up huge ramps(坡道)so all the kids could practice skateboarding and roller blading. How fun！

    Jackson loved his tour of the White House. He was just sorry that he did not get to see the living parts of the President's family. He wondered if the President had to make his bed every day！

China's in﹣orbit Shenzhou﹣16 crew （全体人员），including Jing Haipeng，Zhu Yangzhu and Gui Haichao（网络直播） the first science class from the Mengtian lab module of the China Space Station for the first time on Thursday. 

It is the fourth lecture of the "Tiangong Class" series，China's space science education program，aiming at encouraging young people to achieve their space dreams. 

During the lecture，the crew showed their living and working environment in the Mengtian lab module （舱）. Connected with the Tianhe core module and Wentian lab module，formed a basic T﹣shape structure of the space station. 

The crew showed several interesting experiments in the microgravity （微重力） environment. For example，they showed how a candle flame （火焰），they explained the law of conservation of momentum （动量守恒） by showing the collision （碰撞）

The crew answered questions from the students in the end. When asked whether space rubbish can be seen from the space station and how the space station protects itself，Jing said that they haven't found any space rubbish so far. He said that space rubbish is harmful to the station，and said that the scientists on the ground will keep an eye on its move. "Once there is a threat （威胁），action would be taken，" he said. The space station is also protected by some special equipment. "Even if we meet space rubbish，" he added. 

The Shenzhou﹣16 crew set off to space on May 30，2023 and returned to the Dongfeng landing site in November of the same year. 

Mmm... chocolate smells so good. They make our mouth water. Where does chocolate come from?

Chocolate is made {#blank#}1{#/blank#} cacao (可可豆). Scientists {#blank#}2{#/blank#}( think) cacao came from Central America to Mexico {#blank#}3{#/blank#}3,900 years ago. But now scientists from Canada found that people in some {#blank#}4{#/blank#}( country ) of South America grew cacao. They firstly grew over 5,000 years ago.

Chocolate is popular around {#blank#}5{#/blank#} world. Let's {#blank#}6{#/blank#}( learn) more about this snack(零食).

The color of dark chocolate is dark brown. It has more cocoa butter(可可油). Cocoa butter is good for  {#blank#}7{#/blank#}( we) teeth(牙齿). White chocolate is very sweet. There {#blank#}8{#/blank#}( be) not any cacao in it. Many people think it is not a {#blank#}9{#/blank#}( really) chocolate. Milk chocolate has a mild flavor(淡味). It is light brown. It tastes sweet.

Some scientists say chocolate has too much sugar (糖 ) and this can give people bad teeth,{#blank#}10{#/blank#} others say eating chocolate makes people feel happy. Also, dark chocolate has less sugar and

fat. It is good for the heart. Guess what? I want to have a box of dark chocolate now!

In ancient times, people's only transportation means（交通方法）were their feet. So it was 1 for them to travel from one place to another. As a result, they knew 2 things about outside world. The world was too big for them to understand. 

With the development of society, more and more transportation means 3 : bicycle, bus, car, train, ship, plane, etc. They carry people to and from every corner of the world. And they make people 4 to each other. 

So it's easier for people from different countries to understand each other, to communicate with each other. So the world is getting smaller and smaller, just like one big 5 .