Studies show farmland in Africa is often lacking in important nutrients. But researchers say combining different farming methods may help. Since the world food crisis several years ago, researchers have directed more of their attention to small farms. Most farms in areas south of the Sahara Desert are only about one or two hectares. One of the goals is to increase production without necessarily clearing more land to grow additional crops. American researchers say that can happen with greater use of an agricultural system called perennation. It mixes food crops with trees and perennial plants - those that return year after year. Mr. Reganold, who is with Washington State University, says poor soil may have resulted from years of weathering that washed away many nutrients. He says some farmers may have done more harm than good. He estimates that up to two billion dollars worth of nitrogen, phosphorous and potassium is lost from African soil each year. The scientist says the word perennation defines three systems that are already used in Africa. The oldest of the three is called evergreen agriculture. This is where farmers plant trees with their crops. John Reganold says farmers in Africa have been doing this for sixty years, but it seems to be growing in popularity. The method is gaining widespread use in countries such as Niger, Burkina Faso, Malawi and Zambia. The trees are planted among maize, millet or sorghum crops. They not only add nitrogen to the soil through their roots, but also through their leaves when they fall off and break down. At other times of the year, the trees can protect plants from strong sunlight. Mr. Reganold was one of three researchers who wrote a report about perennation. It was published in the journal Nature. This report is mostly likely to be a journal of _ . A) food B) environment C) agriculture D) gardening
C
The Lego Group had a very low beginning in the workshop of Ole Kirk Christiansen,a carpenter from Denmark.Christiansen began creating wooden toys in 1932.Two years later, he came upon the Lego name by putting together the first two letters of the Danish words Leg and Godt,which mean "play well."The name could be interpreted as "I put together" in Latin;it is also similar to the Greek verb meaning "gather" or "pick up". In 1947,the company enlarged to making plastic toys.At first,the use of plastic for toy production was not highly regarded by salesmen and consumers of the time.Many of the Lego Group's shipments were returned,following poor sales.However, Christiansen's son,Godtfred Kirk Christiansen,saw the great potential in Lego bricks to become a system for creative play-As the junior managing director of the Lego Group,he spent years trying to improve the "locking" ability of the bricks and made the bricks more versatile .In 1958, the modem interlocking brick design was finally developed and patented . Today Lego is sold in more than 1 30 countries.Every minute 33,824 Lego bricks are made,and kids around the world spend 5 billion hours a year playing with Lego.There will be more than 400 million people playing with Lego bricks this year.On average,every person in the world owns 62 Lego bricks,and about seven Lego sets are sold every second. This year Lego fans all over the world are celebrating the 50th anniversary of the tiny building blocks.Though already 50 years old,Lego is still the same product it was in the 1950s. Bricks bought then are still compatible with present bricks and that is probably the reason the toy has never fallen out of favor. What is most likely the reason why Lego still remains popular? A) Old Lego bricks may still be connected to new ones. B) The company hasn't changed its name since 1 947. C) The material for the bricks has proved to be safe. D) The price of the toy is ly reasonable.
A
(Question)
Teachers say the digital age has had a good influence - and a not-so-good influence - on this generation of American teenagers.More than 2,000 teachers took an online survey.Three-quarters of the teachers said the Internet and digital search tools have had a "mostly positive" effect on their students' research habits and skills.But 64 percent said the technologies "do more to distract( - - - ---) students than to help them academically." And 87 percent agreed that these technologies are creating an "easily distracted generation with short attention spans." The Pew Internet Project did the survey with the National Writing Project.Judy Buchanan is the vice director of the National Writing Project and a co-author of the report.Ms.Buchanan says digital research tools are helping students learn more and faster."Teachers really favor these tools because they are ways to make some of the learning exciting and engaging.Young people favor these tools.The goal is to really help them become creators of meaningful content, and not just sort of consumers." But one problem the survey found is that many students lack digital literacy.They trust too muck of the information they find on the Internet.Judy says these students haven't developed the skills to determine the quality of online information."It's something that really has to be taught and paid attention to.Because in a world in which things happen quickly, you do need to step back, reflect and analyze the information you have." Another problem is blamed on something that might not seem like a problem at all: being able to quickly find information online.Teachers say the result is a reduction in the desire and ability of their students to work hard to find answers.They say students are overly dependent on search engines and do not make enough use of printed books or research libraries. Many teachers are also concerned that the Internet makes it easy for students to copy work done by others instead of using their own abilities. Some students don't tend to work hard because A) they can get answers on the Internet quickly B) printed books and libraries around aren't enough C) the Internet can't make students concentrate D) they can copy each others' work without being punished
(Answer)
A