(1)Substantial changes in the nation’s mad cow testing system were ordered yesterday after British tests on a cow slaughtered in

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问题     (1)Substantial changes in the nation’s mad cow testing system were ordered yesterday after British tests on a cow slaughtered in November confirmed that it had the disease even though the American "gold standard" test said it did not.
    (2)"The protocol we developed just a few years ago to conduct the tests might not be the best option today," Agriculture Secretary Mike Johanns said in making the an-nouncement. "Science is ever evolving."
    (3)At an afternoon news conference in Washington, Mr. Johanns described serious errors in the testing in the United States on the animal, the second one found with mad cow disease, formally known as bovine spongiform encephalopathy.
    (4)But he also defended the safety of American beef, reminding reporters that the animal had been incinerated rather than being ground into hamburger, as the first one was in late 2003.
    (5)"I enjoyed beef this noon for lunch," Mr. Johanns said. "It is the safest beef in the world."
    (6)The head of the testing laboratory in Weybridge, England, who joined the news conference by telephone, said he was "pretty confident" that the incidence of mad cow disease in American herds was "very little indeed"
    (7)Of 388,000 tests in the last year, only three positive rapid tests have been found, and only this one has been confirmed.
    (8)Until yesterday, the Agriculture Department used a rapid test called an Elisa and confirmed any positives with a slower immunohistochemistry test, which it calls the "gold standard."
    (9)The Europeans and the Japanese use those tests, but routinely add a confirmatory Western blot test, which is more sensitive.
    (10)The Agriculture Department asked the English laboratory, regarded as one of the world’s best, to retest the samples.
    (11)In response to questions, Dr. John Clifford, the Agriculture Department’s chief veterinarian, revealed another surprise: the animal’s disease strain did not closely resemble the British-style strain found in the first mad cow, which was born in Canada and raised in Washington State.
    (12)Instead, it was closer to a strain found in France—a result, another scientist said, that suggested that the infection had come from a different pool of infected feed, possibly imported from France.
    (13)Despite the Agriculture Department’s assurances, critics said the dispute revealed serious flaws in the testing regimen used here for 15 years.
    (14)"All this foot-dragging has got to stop," Michael K. Hansen, a senior research associate at Consumers Union, said excitedly.
    (15)"They waited seven months to do this test?" Dr. Hansen asked. "And they didn’t even bother to write up a report?"
    (16)Like other critics, Dr. Hansen called for testing all animals over 20 months old, and for bans on feeding poultry litter that has spilled cattle meal in it back to cattle, giving calves "milk replacer" made from cattle blood and letting cows eat dried restaurant "plate waste."
    (17)Dr. Hansen said the feed bans that the department refers to as its "firewall" were "more of a white picket fence."
    (18)Mr. Johanns refused to give details about the animal, other than to repeat that it was born before the 1997 ban on feeding ruminant protein to ruminants, mat it was raised for beef, not dairy, and mat it was too crippled to walk when it was killed.
    (19)There was "no evidence" mat it was born outside me United States, Mr. Johanns said, and its brain was sampled for tests at a plant specializing in diseased and dead animals. Most beef animals are slaughtered when they are less than 3 years old.
    (20)DNA tests will be started to find me herd it was raised with, Mr. Johanns said. Normally, an infected animal’s whole herd is slaughtered on the assumption that all ate the same feed.
What is the main idea of this passage?

选项 A、American beef is 100% safe in the world due to me excellent testing system
B、US government should make sure that me beef in the market is safe enough.
C、American "gold standard" should not be in use any more due to serious errors in it.
D、Europeans and Japanese recognized the sensitivity of mad cow disease testing system.

答案C

解析 本题考查全文中心思想。原文首段即可视作全文的主题句。文章后面的内容都是对此主题句的解释和延伸,所以选项C“由于美国的‘黄金标准’检测方法有严重错误不应再被使用”是正确答案。
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