阅读理解

　　Last Wednesday, Agriculture Secretary Ann Veneman announced the first case of mad cow disease in the United States. A test seemed to show bovine spongiform encephalopathy, or B-S-E, in a cow from Washington state. The next day, a laboratory in Waybridge, England, confirmed (proved) the case.

　　Within hours of the news, Japan, Mexico and South Korea had banned(禁止) imports(进口) of American beef. More than thirty nations have now banned American beef imports. The restrictions(限制) affect about ninety percent of American beef exports worth about three-thousand-million dollars a year.

　　American agriculture officials say that the nation's supply of beef is safe. They note that only the brain and nerve(神经) matter from the cow can carry B-S-E. They say infected(受感染的) parts of the cow were not processed(加工) for use as food for people.

　　On Saturday, the top animal doctor for the United States Agriculture Department said the infected cow came from Alberta, Canada. Ron De Haven said the cow was in a group of seventy-four animals bought from Canada two years ago. But a Canadian official noted that Canada's records do not match the American ones. He said there was no clear evidence(证据) that the infected cow came from Canada.

　　So far, almost five-thousand kilograms of beef have been seized. American officials have temporarily(暂时) closed two farms where the infected cow had been kept and where its half is believed to be.

　　The situation is harming American beef producers. In May, Canadian officials reported a single case of B-S-E in Alberta. Many nations, including the United States, banned Canadian beef. That ban cost Canada one-million dollars a day.

　　American beef prices are quickly dropping. An American delegation went to Japan to try to ease fears. Japan has suggested that the United States should expand its B-S-E testing program. Japan tests every cow for the disease.

　　B-S-E is widely known as mad cow disease. It is caused by deformed proteins(蛋白质) called prions. B-S-E spreads when animals eat food containing processed brains or nervous tissue of infected animals.

　　A form of B-S-E, Cruetzfeldt-Jakob disease, infects people. Reports say about one hundred and fifty people have died from the disease, mostly in Britain, since B-S-E was first identified in nineteen eighty-six.

1．Where did America's first case of mad cow disease come from?

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2．What effects does mad cow disease have on America's exports?

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A．So far no country has banned the imports of American beef.

B．More than 30 countries have banned the imports of American beef.

C．No American beef will be imported into any foreign country.

D．it will cause American beef exports a great loss of about 3,000 million dollars a month.

3．Which of the following statements is NOT true?

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A．It is believed that now American supply of beef is still safe.

B．The brain and nerve matter of an infected cow is mostly like to carry B-S-E.

C．American beef prices will not drop quickly.

D．Cruetzfeldt-Jakob disease can do great harm to people's health.

4．What does the underlined word “ease” mean in the last but two paragraph?

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A．To reduce pain or worry.

B．To make somebody happy.

C．To become less troublesome or difficult.

D．To take away pain or worry.