only a half million years ago 59. A million years are added to man s past by the A. unearthing(出土) of Zinjanthropus B. discovery of some primitive tools C. dating of rock samples from East Africa D. invention of a radioactive dating process This leads anthropologists to believe that A. the pattern of human evolution was not what has been generally supposed B. the evolutionary pace was faster than was supposed C. primitive intelligence must be reevaluated D. previous theories of human evolution are correct The Zinjanthropus can be called a man because A. it made and used tool B. it walked erect C. its brain directed its too making D. it probably communicated by speech The new date fits the human evolutionary pattern more easily than the old because A. allows a more reasonable evolutionary pace B. indicates man is younger than was believed C. establishes the existence of man in the Pliocene Age D. indicates that man is nearly two million years old Passage 4 Magic bullets", this term sounds like the invention of a fantasy writer, but in fact, it represents a long standing dream of medical scientists. The dream: to find ways of homing in on and destroying diseased cells, such as cancer cells, while leaving heal thy cells unharmed. It is a tantalizing idea but a highly elusive one, and for years reseachers could not quite make t work The search for magic bullets began early in this century with the work of a brilliant German bacteriologist, Paul Ehrlich, who coined the term magic bullets, noticed that certain dyes were taken up by a variety of infectious microorganisms. That observation led him to the idea of chemically hitching a toxin (poison)such as arsenic to a dye to kill the microbes(germs)that cause yphilis and other diseases. Al though his efforts had only limited success, they led to the concep of "chemotherapy", the use of chemicals to treat disease. In later years, other investigators began looking for chemicals to kill cancer cells that have metastasized, or spread to other parts of the body. Metastasis is what makes cancer so deadly. A cancerous tumor can be removed surgically. But if even one or two cancer cells have broken away from a tumor, they can travel through the circulatory system and start new tumors elsewhere in the body. By the 1980 s, researchers had deve loped some 40 drugs for killing cancer cells. These chemicals generally act by entering and destroying cells that are in the process of dividing rapidly. The problem is that many normal cells, such as hair cells and the cells of the intestines(B,), also reproduce rapidly, and so they too absorb a large dose of the chemical. That s why cancer patients receiving chemotherapy often experience hair loss, nausea, and other unpleasant side effects. That is why chemotherapy usually does not cure a patient with metastasized cancer. If enough of the drug is given to kill all the cancer cells, the drug may well kill the patient, too. 63. As we can see from the passage, the " magic bullet"really refers to A. a kind of chemicals B. a kind of instrument C. a specific kind of cell D, a way of treatment In treating cancer patient, chemotherapy A. has proved to be effective B. has no effect at allonly a half million years ago. 59. A million years are added to man's past by the _____ . A．unearthing(出土)of Zinjanthropus B．discovery of some primitive tools C．dating of rock samples from East Africa D．invention of a radioactive dating process ▪ This leads anthropologists to believe that _____ . A．the pattern of human evolution was not what has been generally supposed B．the evolutionary pace was faster than was supposed C．primitive intelligence must be reevaluated D．previous theories of human evolution are correct ▪ The Zinjanthropus can be called a man because _____ . A.it made and used tools B.it walked erect C.its brain directed its toolmaking D.it probably communicated by speech ▪ The new date fits the human evolutionary pattern more easily than the old because it _____ . A．allows a more reasonable evolutionary pace B．indicates man is younger than was believed C．establishes the existence of man in the Pliocene Age D．indicates that man is nearly two million years old Passage 4 “Magic bullets”,this term sounds like the invention of a fantasy writer, but in fact, it represents a long standing dream of medical scientists. The dream: to find ways of homing in on and destroying diseased cells, such as cancer cells, while leaving healthy cells unharmed. It is a tantalizing idea but a highly elusive one, and for years reseachers could not quite make it work. The search for magic bullets began early in this century with the work of a brilliant German bacteriologist, Paul Ehrlich, who coined the term magic bullets, noticed that certain dyes were taken up by a variety of infectious microorganisms. That observation led him to the idea of chemically hitching a toxin(poison)such as arsenic to a dye to kill the microbes(germs)that cause syphilis and other diseases. Although his efforts had only limited success, they led to the concept of“chemotherapy”,the use of chemicals to treat disease. In later years, other investigators began looking for chemicals to kill cancer cells that have metastasized, or spread to other parts of the body. Metastasis is what makes cancer so deadly. A cancerous tumor can be removed surgically. But if even one or two cancer cells have broken away from a tumor, they can travel through the circulatory system and start new tumors elsewhere in the body. By the 1980's, researchers had developed some 40 drugs for killing cancer cells. These chemicals generally act by entering and destroying cells that are in the process of dividing rapidly. The problem is that many normal cells, such as hair cells and the cells of the intestines(肠),also reproduce rapidly, and so they too absorb a large dose of the chemical. That is why cancer patients receiving chemotherapy often experience hair loss, nausea, and other unpleasant side effects. That is why chemotherapy usually does not cure a patient with metastasized cancer. If enough of the drug is given to kill all the cancer cells, the drug may well kill the patient, too. 63. As we can see from the passage, the“magic bullet”really refers to _____ . A．a kind of chemicals B．a kind of instrument C．a specific kind of cell D．a way of treatment ▪ In treating cancer patient, chemotherapy _____ . A．has proved to be effective B．has no effect at all