In San Francisco, there is a special group of volunteers. They call themselves Friends of the Urban (城市的) Forest (FUF). These volunteers want to {#blank#}1{#/blank#}. Every year, the FUF plants nearly 1,000 trees.

The FUF welcomes new volunteers all year round and in all parts of its work. On Weekend Planting Days, FUF volunteers work with common citizens (市民) to plant trees. The planting usually runs from 9 a.m. to 1 p.m. After the work is done, everyone {#blank#}2{#/blank#} over a community lunch.

On Thursday Planting Days, the FUF plants "replacement (替换) trees". As their name suggests, these trees replace trees {#blank#}3{#/blank#}. Planting Leaders are very experienced volunteers. They are able to help other volunteers at planting events. Planting Leaders usually wear a special FUF T-shirt. Some new volunteers know little about "replacement trees". They can easily find Planting Leaders and {#blank#}4{#/blank#}.

A tornado (龙卷风) is a kind of strong storm with air which moves in a circle quickly. They can move over 200 miles per hour and cause a lot of damage (损坏). As they move across the land, they can easily pick up cars, trucks, and even houses, and then throw them very far. It is important to find a safe place if a tornado gets close.

A safe place could be a basement ( 地下室) or the lowest floor. If you are in a home without a basement, try to find a first-floor bathroom or a small room without windows in the middle of your house. You should curl up (蜷缩) into a ball and cover your head and neck with your hands.

But there are some people who actually want to get close to tornadoes. They are scientists who want to learn more about tornadoes. One of the best ways to do this is to get as close as possible to the tornado. They use special tools to measure (测量) what is happening in and around a tornado.

One special tool is called a tornado probe ( 探测仪). Inside the tornado probe, there are sensors (传感器) to measure wind speed, temperature, pressure, and direction.

Some probes even have cameras, so the scientists can see and understand what it's like to be in a tornado.

To be able to get these measurements, the scientists have to get a tornado probe near or into a tornado. Scientists will try to guess where a tornado will go next. Then they drive to that location and put down the probe. If they do not guess correctly, they pick up their probe and try another place. If they are right, the tornado will go near or even right over the probe. Then they take all of the measurements

from the probe and use them to predict where future tornadoes may form (形成) and travel. And they can give people some warning to keep away from a dangerous tornado.

The traditional Chinese lunar calendar divides the year into 24 solar terms (节气). They mark the changing seasons and agricultural cycles (农业周期). Among the 24 solar terms, Xiaoman, the eighth solar term, falls around May 20th or 21st each year.

The name "Xiaoman" means "little full" in Chinese, showing the fact that the foods in the field are beginning to be full, but they are not yet ripe. It's a time when farmers can watch their fields turn golden under the warm spring sun. They hope to have a good harvest (丰收) soon in autumn.

During Xiaoman, the weather gradually changes from spring to summer. The days become longer and hotter, and the rainfall increases, providing the necessary water for food growth. This period is important for farmers, as it can influence the quality of their harvest.

A special custom related with Xiaoman is silkworm raising (养蚕) . Silkworm raising is an important way to make a living for people who live in south of the Yangtze River, especially in Jiangsu and Zhejiang provinces. The ancient Chinese believed that Xiaoman is the birthday of the god of the silkworm. Silkworms need to be taken good care of at this time of the year with the fresh mulberry (桑 葚) leaves. It's also regarded as the best time to cook cocoons (茧) and produce silk. Famous Chinese poets such as Li Bai and Du Fu from the Tang Dynasty (618-907), and Su Shi from the Song Dynasty (960-1279) all wrote poems that described the silkworm raising activities at that time, such as silk reeling.

Today, it's popular for Chinese children to raise white silkworms in a paper box, covered with green fresh mulberry leaves. For them, raising silkworms is not a way to make a living, but to see the magic of nature. It's exciting to carefully watch the silkwormsgrow bigger and bigger, and finally become white cocoons.

My name is Tony, and I am in Beijing. I like to be busy after school. I can always find some interesting things to do. 

I come to a new school this term. This school has many clubs and I want to join some clubs. Ireally like music. I can play the piano and I can play it well. So I want to join the music club. Iwant to play at the school party one day. I'm also good at drawing pictures. Art is my favourite subject. So the art club is fine for me, too. Many people like Picasso's pictures, but I don't like them, because they are very strange(奇怪的). I speak English and I can speak a little Chinese, soI also want to join the Chinese club. 

Many people in Western countries think that everyone in China knows how to do Kung Fu This is not a fact (事实), of course. But it is {#blank#}1{#/blank#}(truly) that Kung Fu is a big part of Chinese culture (文化).

Like many people, I {#blank#}2{#/blank#}(one) learned about Kung Fu by watching the movies. {#blank#}3{#/blank#}(act) like Bruce Lee and Jackie Chan made Kung Fu popular. People {#blank#}4{#/blank#}(begin) to know them by their acting in the movies.

However, I started to feel interested in Kung Fu because {#blank#}5{#/blank#}a hip-hop(嘻哈乐) group, Wu-Tang Clan. It is one of my favorite rap groups, and it is one of {#blank#}6{#/blank#}big) hip-hop groups in history. They often rap about different kinds of Kung Fu.

I do not practice Kung Fu. {#blank#}7{#/blank#}, the ideas behind Kung Fu are interesting. There is a saying by Bruce Lee that I {#blank#}8{#/blank#}(real) like. "Be formless (无定形的. . . . . ) . . . shapeless (不成形的. . . . ), like water, " he once said. He meant to tell each of us that we should change {#blank#}9{#/blank#}(we) when we face difficulties. "I think this is {#blank#}10{#/blank#}excellent way to live a life.

 The concept of dynamic pricing is simple— and easy for businesses to implement. Whether it's a Friday-evening fight, a hotel during the holidays, or a taxi ride in a storm, we have all been burned by higher-than-normal prices due to excess demand. Raising costs when businesses are busiest is the norm(常态) across the travel industry. Perhaps the most well-known example of this is within ride-share companies, which have used surge pricing(峰时定价) for years to charge riders when demand for cars increases rapidly compared to the number of drivers available.

 Outside travel, online stores are increasingly using this dynamic pricing, too, says Vomberg. "On Amazon.com alone, millions of price changes occur within a day, corresponding to (对应于) a price change of about every ten minutes for each product." While consumers might not always pick up on these little changes in price, Vomberg says time-based dynamic pricing will likely become a competitive standard at least in online markets. "AI-enabled tools can suggest the best prices via machine learning algorithms(算法). They can also track and learn competitor and customer responses to price changes," he says.

 Now, surge pricing is happening in stores including bars and supermarkets as well. "Physical businesses are adopting electronic shelf labels that enable real time price adjustment depending on the time of day, stock levels and whether items are approaching their sell-by date," says Sarwar Khawaja, chairman of the Oxford Education Group. He says this technology is likely to cause prices in bars that use these signs to increase during the rushes of dinner, weekends or holidays, or for supermarkets to adjust prices throughout the day or week, depending on the number of shoppers.

 The current economic climate is also driving the need for these pricing technologies. While creating competitive prices is always key to healthy profit margins(利润率), Khawaia says dynamic pricing enables businesses to optimize (使优化) their pricing depending on the financial situations of their customer base. "Businesses can offer discounts during downturns while increasing prices in better off areas," he says.

 The changes, however, may not sit well with consumers. "Dynamic and surge pricing will likely expand to more industries and more companies in the long term, but just because a product may be popular does not mean that customers are willing to turn a blind eye to being charged more," says Khawaja. He adds surge pricing can cause customers to lose faith in a company if they believe they are being overcharged. "Perhaps dynamic pricing of a drink in your favourite pub might be a step too far for loyal customers."