Vienna is a beautiful old city on the River Danube in the center of Europe. It's the capital city of Austria and the center of European classical music. In the 18th century a lot of musicians came to study and work in Vienna.

    In the Strauss family, there were two composers called Johann Strauss: the father and the son. The father, Johann Strauss the elder, wrote and played music for traditional dances, called the waltz. His dance music made him famous all over Europe. The son, Johann Strauss the younger, was also very successful and popular. He wrote over 150 waltzes. In 1867 he wrote The Blue Danube waltz.

    Mozart was another very important composer. He was born in Austria in 1756. Before he was six, he played not only the piano but also the violin. His family took him around Europe and he gave concerts in many cities. He wrote hundreds of wonderful pieces of music. But he became very poor and died in 1791 when he was only 35. Like Johann Strauss, father and son, he was a great European musician, and many people still think his music is perfect.

We rely on our memory for sharing stories with friends or learning from our past experiences. Yet evidence shows that our memory isn't as consistent as we'd like to believe.

There are countless reasons why tiny mistakes might happen each time we recall past events. And whenever these mistakes happen, they can have long-term effects on how we'll recall that memory in the future.

Take storytelling for example. When we describe our memories to other people, we might ask ourselves whether it's important to get the facts straight, or whether we only want to make the listener laugh. And we might change the story's details depending on the listener's attitudes. It isn't only the message that changes, but sometimes it's also the memory itself. This is known as the "audience-tuning effect", showing us how our memories can change automatically over time, as a product of how, when, and why we access them.

In fact, sometimes simply the act of repeating a memory can be exactly what makes it easy to change. This is known as "retrieval-enhanced suggestibility". In a typical study of this effect, participants watched a short film, then took a memory test a few days later. But during the days between watching the film and taking the final test, two other things happened. First, half of the participants took a practice memory test. Second, all of the participants were given a description of the film to read, which contained some false details. Participants who took a practice memory test shortly before reading the false information were more likely to reproduce this false information in the final memory test.

Why might this be? One theory is that repeating our memories of past events can temporarily make those memories malleable. In other words, retrieving（找回）a memory might be a bit like taking ice-cream out of the freezer and leaving it in direct sunlight for a while. By the time our memory goes back into the freezer, it might have naturally become a little misshapen, especially if someone has influenced it purposely in the meantime.

These findings lead us to wonder how much our most treasured memories have changed since the very first time we remembered them. Remembering is an act of storytelling, after all. And our memories are only ever as reliable as the most recent story we told ourselves.

 During lunchtime in Shenzhen, workers often line up to buy food from street vendors(小贩). But in the past, they weren't allowed to set up their stalls(摊位) anywhere on the streets in China. The stalls were believed to be bad for the image of a city." We have to keep the streets clean and tidy," the city government of Beijing once said.

 Things, though, began to change in recent months. In March, Shanghai and Hangzhou worked out detailed plans for stall businesses. And now Shenzhen is also preparing to welcome back street vendors. On April 28, it announced new guidelines on the management of street vending. Under the rules, street vendors will be allowed to operate in certain areas within the city. The new rules worked out on September 1,2023.

 Most people are glad to see vendors getting back on the streets."I think it's good and convenient," said one user on Weibo." Vendors can make money, while customers will have more choice."

 Street vending has long been considered as a lowly job in China. But in 2020, former Premier Li Keqiang pointed out that street vendors were the" lifeblood" of the country. Since then, many Chinese young people have seen the business as a way to get away from the stress of traditional work culture. Some of them can now be seen setting up stalls on weekends in Shanghai.