Printed circuit boards are vital components of modern electronics. However, once they have served their purpose, they are often burned or buried in landfills, polluting the air, soil and water. Most concerning are the flame retardants （阻燃剂）added to printed circuit boards to keep them from catching fire. Now, researchers reporting in ACS Sustainable Chemistry & Engineering have developed a ball-milling method to break down these potentially harmful compounds enabling safer disposal （处理）.
Composed of 30% metallic and 70% nonmetallic particles, printed circuit boards support and connect all of the electrical components of a device. Metallic components can be recovered from circuit boards easily using traditional methods leaving behind nonmetallic particles including those flame retardants and other additives. Scientists have found that compounds in those flame retardants can do harm to people's health, especially to those women who are pregnant. Therefore researchers have been wanting to develop a new method to remove the flame retardants from waste printed circuit boards so that they wouldn't do harm to people and the environment.
The researchers broke down printed circuit boards and removed the metallic components. Then，they put the nonmetallic particles into a ball mill — a rotating （旋转的）machine that uses hard stone balls to make materials into very small pieces. They also added iron powder, which prior studies had shown was helpful for removing chemicals from organic compounds. After ball-milling, the harmful chemicals on the surface of the particles had decreased by 50%・ The researchers determined that during the ball-milling process, iron transferred electrons to flame retardant compounds causing the internal structure to stretch and break.
The authors acknowledge funding from the 111 Project, the Natural Science Foundation of Guangdong Province, China and the Pearl River Star of Science and Technology.
1.People are concerned most about the flame retardants because
A.they are harmful and hard to remove B.they keep circuit boards from catching fire
C.they make up the largest part in electronics D.they are mixed up with other components
2.What is the function of the printed circuit board?
A.Making electronics small and light. B.Preventing electronics catching fire.
C.Connecting all electrical components, D.Allowing easy disposal after being used,
3.What does the author mainly intend to tell us in paragraph 3?
A.How to operate the ball milk B.The ball-milling process and its result.
C.The high efficiency of the new method. D.Why iron powder is added to the process.
4.What can we infer from the last paragraph?
A.The authors are short of money.
B.Over 100 projects support the authors,
C.The researchers will make much money.
D.The ball-milling method is promising.
Lions are most successful at hunting animals during the darker period of the moon’s cycle. But how those prey (猎物) respond to changing threats as the night’s light changes throughout a month has been a mystery. Scientists spied on four of the lions' favorite prey species for several years. They fixed 225 cameras across an area. When animals came by, the cameras responded by taking their pictures.
The prey — wildebeests (角马), zebras, gazelles (瞪羚) and buffalo — are all plant eaters. To meet their food needs, such species must searching for food frequently, even at night. The cameras showed that these species respond to changing risks across the lunar cycle in different ways.
Common wildebeests, which make up a third of the lion’s diet, were the most sensitive to the lunar cycle. These animals appeared to set their plans for the entire night based on the moon’s change. During the darkest period of the month, they’d park themselves in a safe area. But as the nights got brighter, wildebeests were more willing to venture into places where run-ins with lions were likely.
Weighing as much as 900 kilograms, the African buffalo are a lion’s most tough prey. They also were least likely to change where and when they searched for food throughout the lunar cycle. But as nights got darker, the buffalo were more likely to form herds (兽群).
Plain zebras and gazelles also changed their evening routines with the lunar cycle. But unlike the other prey these animals reacted more directly to changing light levels across an evening. Gazelles were more active after the moon had come up. Zebras were sometimes up and about and doing things before the moon had risen.
These behaviors show the wide-reaching effects of moonlight. It offers a very clear example of how the presence or absence of the moon can have fundamental, ecosystem-level impacts.
1.What can we infer from the first paragraph?
A.Lions are excellent night hunters. B.How lions hunt has always been a mystery.
C.Moonlight is a threat to the lion’s prey. D.Lion’s prey likes hunting for food at night
2.What do wildebeests usually do when there is no moon at night?
A.Look for food. B.Wander in the filed
C.Stay in a safe place. D.Explore dangerous places.
3.How do buffalo deal with the risk from lions when it is darker?
A.They stay still at a place. B.They troop to search food.
C.They ignore the lion. D.They change places frequently.
4.Which part of the site might this article come from?
A.Food. B.Animal.
C.Astronomy. D.Environment.
Even if you’ve never been to Phoenix, you know this about the place: It’s hot. But that doesn't stop hikers from attempting the 1.3-mile trek (跋涉) to the top of the city’s famed Camelback Mountain. Signs warn that the trail is “extremely difficult”. If you continue, a posted checklist suggests at least a liter of water per person. And if you keep climbing, another sign farther up declares; “If you’re halfway through your water turn around!”
Unfortunately, many people do not pay attention to the warnings. Fortunately, Scott Cullymore does. The 53-year-old man hikes up and down Camelback a couple of times a day giving out cold bottles of water to worn-out hikers. He has helped so many hikers that he has earned a heavenly nickname: the Water Angel. I’d like a more manly name, but, you know, he told azfamily, com.
Cullymore was on Camelback Mountain one day in 2015 when a British tourist died after being lost for nearly six hours in the July heat. That experience inspired him to start helping people caught unaware by Arizona’s unforgiving version of Mother Nature. “They underestimate the mountain, and they overestimate what they can do, and they get themselves in trouble,” he told the Arizona Republic. If a hiker has a red face and is not sweating anymore, Cullymore reaches into his insulated (隔热的) backpack, pulls out a frosty bottle, and hands it to the person. “It’s misleading that we’re in the middle of the city. You can die up here, and no one would know.”
One hiker who received Cullymore’s water agrees. “You think you know the heat, but then you get out here in the desert and it surrounds you like a blanket,” he said, pointing to Cullymore, “but we are lucky, we run into this good man here.” And with that, the Water Angel goes in search of another hiker in need.
1.What is the purpose of the signs along the hike way?
A.To show the trek is difficult. B.To warn hikers to take enough water.
C.To frighten people to give up. D.To avoid hikers getting lost.
2.What does Scott Cullymone think of his nickname?
A.It’s womanish. B.It’s manly.
C.It’s ironic, D.It’s appropriate.
3.Who will Scott offer his help to?
A.Anybody he meets. B.Those in the middle of the trek.
C.Anyone in need of water. D.Those who sweat a lot.
4.What can be the best title of this text?
A.A Desert-Like Mountain B.Fighting against Heat
C.Necessities for Hiking D.Water Angel
Amsterdam Destination Guide
Amsterdam is one of the most popular travel destinations in the world, famous for its beautiful canals, top art museums and cycling culture.
Must-See Attractions
Most visitors begin their Amsterdam adventure in the Old Centre, which is full of traditional architecture, shopping centers and coffee shops. Don't miss the Dam Square and the areas around Spui and Nieuwmarkt. You'll also want to check out Amsterdam's Museum Quarter in the South District，which is great for shopping and having a picnic in the Vondelpark, The top museums to visit are the Rijksmusuem, the Ann Frank House, and the Van Gogh Museum.
If You Have Time
There are several other unique districts in Amsterdam, and you should try to explore as many of them as time allows. The Canal Ring is a UNESCO World Heritage Site that was originally built to attract wealthy home owners and is a center for celebrity spotting and nightlife today. The Plantage area has most of the city's museums, including the Jewish Historical Museum，the Scheepvaart Museum，and the botanical gardens.
Transportation
Travelers should be aware that Amsterdam Airport Schiphol is one of the busiest airports in the world. This airport is located about 15 kilometers southwest of city center. You can catch a train from Schiphol to Amsterdam Central Station, which has many connecting routes. It's typically not a good idea to drive a car to the city center because traffic is very busy and parking is difficult to find. Cycling is incredibly popular here, and it's easy to find cheap bike rentals around town. Amsterdam has a flat place and is a great city to explore on foot.
Recommended Restaurants
Amsterdam is a top destination for foodies，so it can incredibly difficult to narrow down your dining choices. You are sure to find a restaurant that suits your taste.
1.Which place do most visitors see first in Amsterdam?
A.The Old Center. B.The Dam Square,
C.Spui and Nieuwmarkt, D.The Museum Quarter.
2.What do we know about the Canal Ring?
A.It was built by rich people. B.It is a beautiful natural river,
C.Many famous people live here. D.Visitors here are all museum lovers.
3.How can you get to the city center from the airport?
A.By bike. B.By train,
C.By car. D.By bus.
假定你是李华，由于新冠病毒（COVII-19/nove1 coronavirus）爆发，你校决定推迟开学，请你给回国度假 的留学生Jack写封邮件，告知此事。内容包括：
1.告知推迟开学；
2.介绍疫情；
3.开学日期另行通知。
注意：1.词数100左右；
2.可以适当增加细节，以使行文连贯。
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假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处语言错 误，毎句中最多有两处。每处错误仅涉及一个单词的增加、删除或修改。
增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。
删除:把多余的词用斜线（\ ）划掉。
修改:在错的词下划一横线，并在该词下面写出修改后的词。
注意：1.每处错误及其修改均仅限一词；
2.只允许修改10处，多者（从第11处起）不计分。
I like reading novels, that has earned me the nickname “novel fan”. I like all kinds of novel and I read them whenever I have time. The stories always attract me when I went into them. Every time a novel is in my hand, I will forget to eat , sleep and even me. My mother is very worrying about me, so she makes a arrangement for my spare time. Sometime, when I am fascinated by the story in a novel, I will read it under my quilt to avoid discovered by my mother. But at recently, my eyesight has become poorer. I have decided to change my habit. I want to be health as well as knowledgeable.
