Is paper money going away?纸币已经过时了吗?(词数450) Within a few months，were going to have a new set of banknotes(纸币). The People' s Bank of China(PBOC)，the central bank，has upgraded the fifth editionof the renminbi(RMB)and will issue them from Aug 30. These bills will have brightercolors and new security features(防伪特征)，which will make printing fake(假的)， 000years. Back in the money even harder. We've been using banknotes for around 1Northern Song Dynasty，Chinese people made the world’s earliest paper money to replace metal coins(金属硬币). These bank notes were called jiaozi. Obviously paper money is cheaper to make and easier to carry -these advantages made it more popular than other forms of money. But now，in the digital(数码的)age，paper money方便的) than not seems to be disappearing for the same reason-what's more convenient(having to carry any money at all?China seems to be heading toward becoming a cashless society. From supermarkets t o street stalls(小摊)，people pay by using the WeChat Wallet andAlipay apps on their mobile phones. Sweden is even closer to a future without paper money. Many Swedish banks no longer even have cash on hand. But there are worries about creating cashless. S ome say it is unfair to the poor and people without much education. It's not easy for them to open bank accounts(账户) or deal with mobile phones. And if all of your money is digital you may lose your money if your accountsare hacked(黑客攻击)Although paper money is in a losing battle with electronic payment in some countries，it's still a big thing in most parts of the world. It maytake a little longer than you think to see it go away.Listen to your books耳朵“阅读”时代来了?（词数260，7分钟）With the development of technology and the internet，there is a new trend in reading audio books. More people are choosing to listen to audio books these days，according to this years national reading report.The report was released by the Chinese Academy of Press and Publication(CAPP).It shows that audio books have become quite popular among most readers. One in three adult listen to audio books. They mainly use popular audio sharing platf0mmS(平台) like Ximalaya.Kids have also been a main driver in the development of audio books. Ximalaya noted that the value of audio book purchases made by those aged 13 to 18 in 2018 increased by 330 percent over that of 2017，the Beijing Evening News reported.In addition，around 26.8 percent of children under 8 years old listen to audio books. Most of them listen at least once a week .Their favorite categories(分类)are “stories for kids” and "poetry reading”One of the reasons audio books have taken off is that people want to get more use out of their free time. China News Service reported. Whether they're at the gym，ona bus，or in bed，people can enjoy reading without a heavy paper book ore-reader. Faster internet speeds mean one can download a whole book in just seconds，according to Wei Yushan，director of CAPP.Audio app content designers have invited broadcasters(播音员) and production(制作) groups to join in content production. Both the quality and number of audio books being offered have greatly improved. More people can find the audio books they like the most，the report says.Follow the subway rules在地铁上吃喝将影响个人信用（词数270， 7分钟）Traveling by subway can sometimes be quite an adventure，especially during rush hour. You have to fight your way into the carriage(车厢)And there are the times when you have to avoid cups of coffee that could spill on you. The smells some passengers food are very strong，too.Since April，the local government of Beijing has been collecting public opinions on the revised(修订的) Beijing Metro Passenger Rules The rules say that if passengers behave in an uncivilized(不文明的) manner while on the subway，they will end up with bad credit(信用)scores or even being banned(禁止) from the subway，Beijing Youth Daily reported.Four kinds of behaviors were added to the revised rules. They include stealing others' seats eating or drinking，riding without paying the fare(车票) and handing out advertisements. W hat's worth mentioning is that people have different opinions regarding eating and drinking on the subway，Guangming Daily reported. The rules state that all passengers e xcept babies and people with certain health issues are not allowed to eat or drink on the subway. People have pointed out that the smell of food and drink can annoy other passengers.However，others question this rule，saying that drinking water should be allowed，as people can get thirsty after long rides on the crowded subway. o They also think it is too harsh(严厉的)to lower some ones social credit score Just for eating or drinking."What problems will it cause if I just quietly eat some food that doesn't have any smell and old on to the packaging(包装) when I'm done?”ha user named DONGCHENY wrote on Sina Weibo.Hippos move silicon河马——自然界硅元素的搬运工（词数280，7分钟）Hippos look a little bit silly，don't you think? They have huge bodies，but small eyes and ears. This contrast(对比) always makes hippos look funny and cute.As it turns out，they play an important role in Africa' s ecosystem(生态系统)as well. Hippos have been keeping silicon， a nutrient for plants and animals，on the move throughout East Africa，Science News reported.Each day， a hippo eats about 36 kg of plants. Most of these plants are rich in silicon. The silicon cycles through their body and finally comes out in their poop. Their poop brings 0.4 tons of silicon into the Mara River，where hippos often poop，according to scientists from the University of Antwerp in Belgium. That's about 76 percent of the river's entire downstream silica(硅石)flow.Silicon is mostly found in sand. Its role in nature is important. The element feeds the growth of a plant called the diatom(硅藻)， which lives in oceans. fresh water and other wet environments. Together，these plants take in carbon dioxide(二氧化碳) from the air and change it into oxygen(氧气. It is estimated that diatoms make at least 20 percent of the oxygen on Earth，according to Live Science.Diatoms also form the base of the food chain. They are eaten by small animals like crabs and snails，which in turn feed bigger animals like otters(水獭)，turtles，and even humans Without diatoms，many ecosystems would face a food shortage.But hippos are threatened(受到威胁)by hunting and habitat(栖息地)loss. Their population decreased by up to 20 percent from 1996 to 2004，Science News reported. If these animals disappear from the Mara River，the diatom population could decrease remarkably.Did you know? Silicon is the second-most abundant丰富的) element on Earth. Only oxygen beats it. It makes up slightly more than27 percent of the Earth’s crust(地壳)nature，silicon usually exists as either an oxide (氧化物) like sand or a silicate (硅酸盐)Lightingup black holes黑洞:探索一小步，人类一大步。