单选题
单选题
Text 1
One of the major problems of nuclear energy is the inability of scientists to discover a safe way to dispose of the radioactive wastes which occur throughout the nuclear process. Many of these wastes remain dangerously active for tens of thousands of years, while others have a life span closer to a quarter of a million years. Various methods have been used to date, but all have revealed weaknesses, forcing scientists to continue their search.
The nuclear process involves several stages, with the danger of radioactivity constantly present. Fuel for nuclear reactors comes from uranium ore, which, when mined,, spontaneously produces radioactive substances as byproducts. This characteristic of uranium ore went undetected for a long time resulting in the death, due to cancer, of hundreds of uranium miners.
The United States attempted to bury much of its radioactive waste material in containers made of steel covered in concrete and capable of holding a million gallons. For a long time it was believed that the nuclear waste problem had been solved, until some of these tanks leaked, allowing the radioactive wastes to seep into the environment. Canada presently stores its nuclear waste in underwater tanks, with the long-term effects largely unknown.
However, plans are under consideration for above-ground storage of spent fuel from reactors. These plans include the building of three vast concrete containers, which would be two stories high and approximately the length and width of two football fields. Other suggestions include enclosing the waste in glass blocks and storing them in underground caverns, or placing hot containers in the Antarctic region, where they would melt the ice, thereby sinking down adverse effect on the ice sheets.
A:discover the characteristic of nuclear process B:discover the nature of uranium ore C:save the life of uranium miners D:store nuclear wastes in underwater tanks
A characteristic of the information age is that______
A:the service industry is relying more and more on the female work force B:manufacturing industries are steadily increasing C:people find it harder to earn a living by working in factories D:most of the job opportunities can now be found in service industry
It seems that mental activities are characteristic of______
A:all plants and animals B:some insects C:human beings D:some machines
Richard Holbrooke, who died at the age of 69 after suffering a ruptured aorta, was not the most universally beloved, but was certainly one of the ablest, ’the most admired and the most effective of American diplomats. He is one of the few of that profession in the past 40 years who can be compared with the giants of the "founding generation" of American hegemony, such as Dean Acheson and George Kennan.
Holbrooke was tough as well as exceptionally bright. He was a loyal, liberal Democrat, but also a patriot who was prepared to be ruthless in what he saw as his nation’s interest. To his friends, he was kind and charming, but he could be abrasive: no doubt that characteristic helped prevent him becoming Secretary of State on two occasions, under Bill Clinton and again when Barack Obama became president.
He held almost every other important job in the international service of the US. He was ambassador to the United Nations, where he dealt with the vexed problem of America’s debts to the organization, and to Germany. He was the only person in history to be assistant Secretary of State—the key level in routine diplomacy—in two regions of the world, Europe and Asia. He distinguished himself as an investment banker, a magazine editor, a charity executive and an author, but he will be remembered most of all for his success in negotiating an end to the war in Bosnia-Herzegovina at an Ohio airbase, and for his part in the American intervention in Kosovo. At the time of his death, he was Obama’s special representative for Afghanistan and Pakistan.
Holbrooke joined the Foreign Service, and in 1963 was sent as a civilian official to Vietnam, where he was one of a talented cohort of young men who were to become leaders in American diplomacy. Once back in Washington in 1966, Holbrooke worked for two years in the White House under Johnson, and then at the State Department, where he was a junior member of the delegation to the fruitless initial peace talks with North Vietnam in Paris.
By 1972, Holbrooke was ready for a change. He became the first editor of the magazine Foreign Policy, created as a less stuffy competitor to the august Foreign Affairs. He also worked for Newsweek magazine. In 1976, he went to work for Governor Jimmy Carter of Georgia, who was beginning his campaign for president and badly needed some foreign policy expertise. When Carter became president, in 1977, Holbrooke became his assistant Secretary of State for Asian affairs. (425 words)
Why didn’t Holbrooke become Secretary of State
A:Because he was a loyal Democrat. B:Because he was strong-minded. C:Because he was rough to his friends. D:Because his characteristic is unique.
Which of the following is a characteristic of thiopental sodium：
A:is administered by intravenous injection B:is used to induce anaesthesia C:causes amnesia D:depresses respiration E:produces marked muscle relaxation
The immune system is equal in complexity to the combined intricacies of the brain and nervous system. The success of the immune system in defending the body relies on a dynamic regulatory communication network consisting of millions and millions of cells. Organized into sets and subsets,these cells pass information back and forth like clouds of bees flying around a hive (蜂巢). The result is a sensitive system of checks and balances that produces an immune response that is prompt, appropriate effective, and self-limiting.
At the heart of the immune system is the ability to distinguish between self and no self. When immune defenders encounter cells or organisms carrying foreign or nonself molecules,the immune troops move quickly to eliminate the intruders(入侵者). Virtually every body cell carries distinctive molecules that identify it as self. The body’s immune defenses do not normally attack tissues that carry a selfmarker. Rather, immune cells and other body cells coexist peaceably in s state known as self-toler-ance. When a normally functioning immune system attacks a nonself molecule, the system has the ability to"remember" the specifics of the foreign body. Upon subsequent encounters with the same species of molecules, the immune system reacts accordingly. With the possible exception of antibodies(抗体) passed during lactation (哺乳期]), this so called immune system memory is not inherited. Despite the occurrence of a virus in your family,your immune system must "learn" from experience with the many millions of distinctive nonself molecules in the sea of microbes (微生物)in which we live. Learning entails producing the appropriate molecules and cells to match up with and counteract each nonself invader.
Any substance capable of triggering an immune response is called an antigen(抗原). Antigens are not to be confused with allergens (过敏原), which are most often harmless substances that provoke the immune system to set off the inappropriate and harmful response known as allergy. An antigen can be a virus, a bacterium or even a portion or product of one of these organisms. Tissues or cells from another individual also act as antigens;because the immune system recognizes transplanted tissues as foreign, it rejects them. The body will even reject nourishing proteins unless they are first brokendown by the digestive system into their primary, nonantigenic building blocks. An antigen announces its foreignness by means of intricate and characteristic shapes called epitopes(抗原表位),which protrude(突 出) from its surface. Most antigens, even the simplest microbes, carry several different kinds of epitopes on their surface; some may even carry several hundreds. Some epitopes will be more effective than others at stimulating an immune response. Only in abnormal situation does the immune system wrongly identify self as nonself and execute a misdirected immune attack.
A:Through an allergic response. B:Through blood type. C:Through characteristic shapes on the antigen surface. D:Through fine hairs protruding from the antigen surface.
A:Through an allergic response. B:Through blood type. C:Through characteristic shapes on the antigen surface. D:Through fine hairs protruding from the antigen surfac
Which is not the characteristic of operating system
A:resource management B:transaction management C:memory management D:disk management
Which is not a characteristic of an RISC processor ( )
A:a high clock speed B:a highly optimized pipeline C:a few general-purpose registers D:a limited amount of small instructions
Which is NOT a characteristic of an RISC processor
A:a high clock speed B:a highly optimized pipeline C:a few general-purpose registers D:a limited amount of small instructions
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