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从事土地评估的中介服务机构必须对土地估价结果独立承担责任，但是要及时将土地估价报告和土地估价业绩清单报国土资源管理部门备查并接受监督。( )
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When El Nino reaches a place, the temperature there would change a great deal.
Some insects rely on the tiny hairs scattered over their bodies to (sense) sound waves.
Scenic Spots on Songshan (嵩山)Songshan has 20 spectacular scenic spots featuring either peaks, caves, waterfalls, springs or woods, all equally majestic and charming. Waterfalls and mist curling around the peaks add much to the beauty of the mountain; peaks are thick with pines which rustle like a murmuring stream in a gentle wind but roar like angry waves when the wind blows hard. The mountain is particularly exquisite in autumn, when most of its trees turn golden and red.Shaoshishan(少室山), the highest peak of Songshan, is a spot not to be missed. The top provides a panoramic view of the surrounding peaks, wave-like forest covered hills and other beautiful sights. In order to reach the top of Shaoshishan, you must run the risk of passing a one-meter- wide passage between the steep cliffs (峭壁), with the help of iron chains along the passage.Songshan is located in Henan province, with beautiful natural scenery and historic spots. While climbing the mountains, you can enjoy the fantastic rocks, ancient trees, charming waters, and many world-famous temples. Seeing from the top of the mountain, you can see the mother river winding away, carries the history of thousands of years.Songshan is located in (46) , with Shao shi shan as its (47) peak. It is beautiful especially in (48) . To reach the top of Shaoshishan, one needs the help of(49) as one goes. One win enjoy the beauty of rocks, trees, (50) and temples. 46（）
On Antibodies Substances foreign to the body, such as disease-causing bacteria and viruses and other infectious agents, are recognized by the body s immune system as invaders. Our natural defenses against these infectious agents are antibodies, proteins that seek out the antigens (抗原) and help destroy them. Antibodies have two very useful characteristics. First, they are extremely specific; that is, each antibody binds to and attacks one particular antigen. Second, some antibodies, once activated by the occurrence of a disease, continue to confer resistance against that disease. Classic example are the antibodies to the childhood diseases of chickenpox(水痘) and measles. The second characteristic of antibodies makes it possible to develop vaccines. A vaccine (痘苗) is a preparation of killed or weakened bacteria or viruses that, when introduced into the body, stimulates the production of antibodies against the antigens it contains. It is the first trait of antibodies, their specificity, that makes monoclonal antibody technology so valuable. Not only can antibodies be used therapeutically(在治疗上), to protect against disease; they can also help to .diagnose a wide variety of illnesses, and can detect the presence of drugs, viral and bacterial products, and other unusual or abnormal substances in the blood. Given such a diversity of uses for these diseased-fighting substances, their production in pure quantities has long been the focus of scientific investigation. The conventional method was to inject a laboratory animal with an antigen and then, after antibodies had been formed, collect those antibodies from the blood serum(血清) (Antibody containing blood serum is called antiserum (抗血清)). There are two problems with this method: It yields antiserum that contains undesired substances, and it provides a very small amount of usable antibody. Monoclonal antibody technology allows us to produce large amounts of pure antibodies. in the following way: we can obtain cells that produce antibodies naturally; we also have available a class of cells that can grow continually in cell culture (培养). If we form a hybrid (混血儿) that combines the characteristic of "immortality"(永生)with the ability to produce the desired substance, we would have, in effect, a factory to produce antibodies that work around the clock. In monoclonal antibody technology, tumor cells that can replicate (重复) endlessly are fused with mammalian cells that produce an antibody. The result of this cell fusion is a "hybridoma" (杂交瘤), which will continually produce antibodies. These antibodies are called monoclonal because they come from only one type of cell, the hybridoma cell; antibodies produced by conventional methods, on the other hand, are derived from preparations containing many kinds of cells, and hence are called polyclonal. An example of how monoclonal antibodies are derived is described below. A myeloma is a tumor of the bone marrow (骨髓) that can be adapted to grow permanendy in cell culture. When myeloma cells were fused with antibody-producing mammalian spleen cells, it was found that the resulting hybrid cells, or hybridomas, produced large amounts of monoclonal(骨髓瘤) antibody. This product of cell fusion combined the desired qualities of the two different types of cells: the ability to grow continually, and the ability to produce large amounts of pure antibody. Because selected hybrid cells produce only one specific antibody, they are more pure than the polyclonal antibodies produced by conventional techniques. They are potentially more effective than conventional drugs in fighting disease, since drugs attack not only the foreign substance but the body’s own cells as well, sometimes producing undesirable side effects such as nausea(恶心) and allergic reactions. Monoclonal antibodies attack the target molecule and only the target molecule, with no or greatly diminished side effects. Which of the following substances is not an invader to the body’s immune system
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