黄色在线观看视频-黄色在线免费看-黄色在线视频免费-黄色在线视频免费看-免费啪啪网-免费啪啪网站

首頁 考試吧論壇 Exam8視線 考試商城 網絡課程 模擬考試 考友錄 實用文檔 求職招聘 論文下載
2013中考 | 2013高考 | 2013考研 | 考研培訓 | 在職研 | 自學考試 | 成人高考 | 法律碩士 | MBA考試
MPA考試 | 中科院
四六級 | 職稱英語 | 商務英語 | 公共英語 | 托福 | 托業 | 雅思 | 專四專八 | 口譯筆譯 | 博思
GRE GMAT | 新概念英語 | 成人英語三級 | 申碩英語 | 攻碩英語 | 職稱日語 | 日語學習 |
零起點法語 | 零起點德語 | 零起點韓語
計算機等級考試 | 軟件水平考試 | 職稱計算機 | 微軟認證 | 思科認證 | Oracle認證 | Linux認證
華為認證 | Java認證
公務員 | 報關員 | 銀行從業資格 | 證券從業資格 | 期貨從業資格 | 司法考試 | 法律顧問 | 導游資格
報檢員 | 教師資格 | 社會工作者 | 外銷員 | 國際商務師 | 跟單員 | 單證員 | 物流師 | 價格鑒證師
人力資源 | 管理咨詢師 | 秘書資格 | 心理咨詢師 | 出版專業資格 | 廣告師職業水平 | 駕駛員
網絡編輯 | 公共營養師 | 國際貨運代理人 | 保險從業資格 | 電子商務師 | 普通話 | 企業培訓師
營銷師
衛生資格 | 執業醫師 | 執業藥師 | 執業護士
會計從業資格考試會計證) | 經濟師 | 會計職稱 | 注冊會計師 | 審計師 | 注冊稅務師
注冊資產評估師 | 高級會計師 | ACCA | 統計師 | 精算師 | 理財規劃師 | 國際內審師
一級建造師 | 二級建造師 | 造價工程師 | 造價員 | 咨詢工程師 | 監理工程師 | 安全工程師
質量工程師 | 物業管理師 | 招標師 | 結構工程師 | 建筑師 | 房地產估價師 | 土地估價師 | 巖土師
設備監理師 | 房地產經紀人 | 投資項目管理師 | 土地登記代理人 | 環境影響評價師 | 環保工程師
城市規劃師 | 公路監理師 | 公路造價師 | 安全評價師 | 電氣工程師 | 注冊測繪師 | 注冊計量師
化工工程師 | 材料員
繽紛校園 | 實用文檔 | 英語學習 | 作文大全 | 求職招聘 | 論文下載 | 訪談 | 游戲
英語四六級考試

星火:2008年12月英語四級模擬試卷樣題及解析

來源:星火 2008-12-4 16:34:01 考試吧:中國教育培訓第一門戶 模擬考場

點擊這里下載WORD版

  Part Ⅰ Writing (30 minutes)

  Directions: For this part, you are allowed 30 minutes to write a short essay entitled The Decrease of Public Transportation Ticket Fare. You should write at least 120 words following the outline given below:

  1. 近來一些城市政府實施多項舉措降低公共交通票價,大力發展公共交通;

  2. 此措施帶來的好處;

  3. 作為市民應如何響應政府的號召。

  The Decrease of Public Transportation Ticket Fare

  Part Ⅱ Reading Comprehension (Skimming and Scanning)(15 minutes)

  Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions on Answer Sheet 1.

  For questions 1-7,choose the best answer from the four choices marked A), B), C) and D).

  For questions 8-10,complete the sentences with the information given in the passage.

  The Debate Over Genetically Modified Foods

  For thousands of years farmers have used a process of selection and cross breeding to continually improve the quality of crops. Traditional breeding methods are slow, requiring intensive labor: while trying to get a desirable trait in a bred species, undesirable traits will appear and farmers must continue the process over and over again until all the undesirables are bred out. In contrast, organisms acquire one specific gene or a few genes together through genetic modification, without other traits included and within a single generation. However, this technology too is inherently unpredictable and some scientists believe it can produce potentially dangerous results unless better testing methods are developed. Traditional breeding is based on sexual reproduction between like organisms. The transferred genes are similar to genes in the cell they join. They are conveyed in complete groups and in a fixed sequence that harmonizes with the sequence of genes in the partner cell. In contrast, bioengineers isolate a gene from one type of organism and collect it randomly into the DNA of a dissimilar species, disrupting its natural sequence. One of the main differences between conventional and genetically modified crops is that the former involves crosses either within species or between very closely related species. However, GM crops can have genes from closely related species or even from bacteria and viruses. Benefits: one side of the debate Economical? GM supporters tell farmers that they stand to reap enormous profits from growing GM crops. It takes a shorter time to produce the desired product. It is precise and there are no unwanted genes. To produce the GM crops, modern biotechnology is used which requires highly skilled people and sophisticated and expensive equipment. Large companies need considerable investments in laboratories, equipment and human resources, hence the reason why GM crops are more expensive for farmers than traditional crops. Herbicide-resistant crops So what other advantages do GM crops hold for farmers? GM crops can be produced to be herbicide (除草劑) resistant. This means that farmers could spray these crops with herbicide and kill the weeds, without affecting the crop. In effect, the amount of herbicide used in one season would be reduced, with a subsequent reduction in costs for farmers and consumers. Biotechnology companies are even experimenting with crops that can be genetically modified to be drought and salt-tolerant, or less reliant on fertilizer, opening up new areas to be farmed and leading to increased productivity. However, the claims of less herbicide usage with GM crops have till now not been independently supported by facts. Better quality foods Even animals can be genetically modified to be leaner, grow faster, and need less food. They could be modified to have special characteristics, such as greater milk production in cows. These modifications again lead to improved productivity for farmers and finally lower costs for the consumers. Modified crops could perhaps prevent outbreaks such as foot and mouth disease, which has badly influenced many farmers and local economies. No such products have been released to date; however, some are under consideration for release. For example, GM salmon, capable of growing almost 30 times faster than natural salmon, may soon be approved by the FDA (Food and Drug Administration) in the U.S. for release into open waters without a single study on the impact on human health or the environment. Risks: the other side of the debate Environmental damage The problem with GM crops is that there is little known about what effect they will have in, say, 20 years time. The genetic structure of any living organism is complex and GM crop tests focus on short-term effects. Not all the effects of introducing a foreign gene into the complex genetic structure of an organism are tested. Will the pests that a crop was created to resist eventually become resistant to this crop? Then there is always the possibility that we may not be able to destroy GM crops once they spread into the environment. Risk to food web. A further complication is that the pesticide produced in the crop may unintentionally harm creatures. GM crops may also pose a health risk to native animals that eat them. The animals may be poisoned by the built-in pesticides. Tests in the U.S. showed that 44% of caterpillars (毛蟲) of the monarch butterfly died when fed large amounts of pollen(花粉)from GM corn. Disease. Another concern is disease. Since some crops are modified using the DNA from viruses and bacteria, will we see new diseases emerge? What about the GM crops that have antibiotic-resistant marker genes? Marker genes are used by scientists to determine whether their genetic modification of a plant was successful. Will these antibiotic-resistant genes be transferred to microorganisms that cause disease? We already have a problem with ineffective antibiotics. How can we develop new drugs to fight these new bugs? Until further studies can show that GM foods and crops do not pose serious threats to human health or the world's ecosystems, the debate over their release will continue. Living organisms are complex and tampering with their genes may have unintended effects. It is in our common interest to support concerned scientists and organizations, such as Friends of the Earth who demand required labeling of these food products and independent testing for safety and environmental impacts.

  1. What is the main difference between conventional breeding and genetic breeding?

  A) The former is based on sexual reproduction between like organisms while the latter can have genes even from bacteria and viruses.

  B) The former is unpredictable while the latter is predictable.

  C) The former is applied by farmers while the latter by scientists.

  D) The former has a long history while the latter a short one.

1 2 3 4 5 6 7 8 9 10  ... 下一頁  >> 
  相關推薦:星火:2008年12月英語六級考試預測試題
       新東方:2008年12月英語六級考試模擬沖刺試卷
       考試吧恩波:2008年12月六級預測試卷及解析(三)
文章搜索
中國最優秀四六級名師都在這里!
趙建昆老師
在線名師:趙建昆老師
   2003年初進入新東方學校,開始接近7年講臺生涯。目前教授課程有:...[詳細]
版權聲明:如果英語四六級考試網所轉載內容不慎侵犯了您的權益,請與我們聯系800@exam8.com,我們將會及時處理。如轉載本英語四六級考試網內容,請注明出處。
主站蜘蛛池模板: h成人在线 | 伦理片中文字幕完整视频 | 成人激情小视频 | 欧美一区二区三区男人的天堂 | 欧美激情精品久久久久久久 | 最近免费最新高清中文字幕韩国 | 欧美日韩在线高清 | 欧美人猛交日本人xxx | 在线观看黄网址 | 欧美午夜视频一区二区三区 | 久久午夜鲁丝片午夜精品 | 色狠狠综合网 | 高清人人天天夜夜曰狠狠狠狠 | 亚洲视频高清 | 成人污视频在线观看 | 麻豆国产在线观看免费 | 国产91精品高跟丝袜在线 | 伊人再现| 多人性激烈的欧美三级视频 | 欧美日韩一级黄色片 | 日韩久草视频 | 成人网址在线观看 | 91免费精品国偷自产在线在线 | 国产成人精品免费视频大 | 欧美最猛性free护士hd | 91精品成人免费国产 | 国产一级特黄高清免费大片 | 麻豆精品在线 | 免费精品国偷自产在线读大二 | 国产一级久久久久久毛片 | 狠狠色婷婷狠狠狠亚洲综合 | www大片| 国产v在线在线观看羞羞答答 | 中文字幕rct931在线视频 | 亚洲综合久久综合激情久久 | 999影院成 人在线影院 | 亚洲午夜久久 | 玖玖玖精品视频免费播放 | 一级全黄毛片 | 免费播放欧美一级特黄 | 正在播放国产一区 |