For many people, Xiaohongshu (Little Red Book) is one of the top sites for tips on beauty, fashion, travel, food and education. For others, it is also a perfect place to share one’s life experiences. But for a growing number of young people, the site is a place to look not for friends, but dazi, or “activity partner”.

The word dazi became especially common earlier this year, with many people in search of those with similar interests. Unlike friendships, the relationships between dazi is not long or deep. The idea is simple—people come together to join in an activity they all enjoy.

Finding dazi circles is becoming popular for two reasons. First, the Internet has made it easy for young people to connect with one another. Second, young people, especially students，usually have smaller social circles.“For students, their friends are mostly their schoolmates. So, it can be difficult to find someone who shares a similar interest. Going online to find dazi to do something they like is more practical” says Xu Shijin, an organizer of dazi groups on Xiaohongshu.

▲     Bu Yu, a 35-year-old who lives in Shanghai, decided to form a dazi group after finding that many mothers wanted their children to play together. She created a group in late March, and organized at our of the Shanghai Firefighting Museum in April with other families that have children of similar ages. “The experience was great,” says Bu.

“We humans like doing things together. This is why young people are crazy about finding dazi circles these days,” says Yu Hai, a professor at Fudan University. It’s also good for young people to take part in more gatherings to practice their social skills.

There are many natural mysteries and wonders in the world, here are some of them.

About 11,000 years ago, some ancient humans went for a muddy walk in Africa. They left more than 400 footprints, which became fossils. It’s the largest collection of ancient African footprints ever found. Scientists have studied all the footprints. And they have learned more about the people who left them. All of the footprints came from feet. Scientists found the footprints of 17 people who probably walked together. The footprints were all traveling in the same direction and at the same speed. From the size of the footprints, scientists think the group was mostly adult women. They may have been out gathering food together.

Can snakes be friends? Some scientists recently found the answer by closely watching 40 young garter snakes. These small, harmless snakes are common in North America. Scientists divided the snakes into 10 groups. Then they put each group into a small space together for eight days. They found that snakes do seem to have friends. Each snake liked to stay together with certain snakes more than others. Even when scientists moved them around, the snakes often went back to their same friends. Snakes are known for being unfriendly — but it’s not always true, scientists say.

All living things need water. But they get it in different ways. You drink water from a glass. Plants take it in with their roots (根). Koalas get water from eucalyptus (桉树) leaves they eat. But scientists have discovered that koalas have another way to get water: They lick (舔) trees. People noticed the surprising behavior while watching wild koalas in Australia. During rainstorms or right after, rainwater dropped down from tree trunks. Some koalas got the running water while they sat in the trees. One koala was so thirsty that it kept licking a wet tree trunk for more than 30 minutes without stopping.

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Long ago, as people got older, there was something wrong with their teeth and they would have a toothache. 【小题1】

Later people learned that cleaning their teeth was important, but they didn’t have toothpaste (牙膏）at that time. 【小题2】

About 100 years ago someone finally invented a kind of cream to clean teeth. Not long after that, the toothpaste tube (管子) was invented, so people could press the toothpaste right onto the toothbrush! 【小题3】The army gave toothbrushes and toothpaste to all the soldiers, and they learned to brush teeth twice a day. At that time toothpaste tubes were made of metal (金属 ). 【小题4】

Today there are plenty of toothpaste choices: lots of colors and tastes to choose from, and some kinds of toothpaste are made just for children. When you are choosing a kind of toothpaste, make sure it has fluoride ( 氟化物). 【小题5】When you brush your teeth, you don’t need a lot of toothpaste: just press out a bit.

Teeth are a very important part of our body. We will lose them forever once they are broken. So we must protect them.