单选题
单选题
The Great Transformation is caused by
A:artificial intelligence and genetic engineering. B:the shortage of natural resources. C:the development of practical science. D:unknown reasons.
The driver who caused the accident ______.
A:drove very, very fast B:killed another driver C:killed himself D:both A and C
The accident was caused by ______.
A:the driver of the first car B:the driver of the second car C:the driver of the third car D:both B and C
A:Some plant diseases may be caused by bacteria. B:Some plant diseases may be caused by pathogens. C:Some plant diseases may be caused by fungus. D:Symptoms are always helpful in identifying diseases.
Diseases of Agricultural Plants
Plants, like animals, are subject to diseases of various kinds. It has been estimated that some 30,000 different diseases attack our economic plants; forty are known to attack com, and about as many attack wheat. The results of unchecked plant disease are all too obvious in countries which have marginal food supplies. The problem will soon be more widespread as the population of the world increases at its frightening rate. Even in countries which are now amply fed by their agricultural products there could soon be critical food shortages. It is easy to imagine the consequences of some disastrous attack on one of the major crops; the resulting famines could kill millions of people, and the resulting hardship on other millions could cause political upheavals disastrous to the order of the world.
Some plants have relative immunity to a great many diseases, while others have a susceptibility to them. The tolerance of a particular plant changes as the growing conditions change. A blight may be but a local infection easily controlled; on the other hand it can attack particular plants in a whole region or nation. An example is the blight which killed virtually every chestnut tree in North America. Another is the famous potato blight in Ireland in the last century. As a result of that, it was estimated that one million people died of starvation and related ailments.
Plant pathologists have made remarkable strides in identifying the pathogens of the various diseases. Bacteria may invade a plant through an infestation of insect parasites carrying the pathogen. A plant can also be inoculated by man. Other diseases might be caused by fungus which attacks the plant in the form of a mold or smut or rust. Frequently such a primary infection8 will weaken the plant so that a secondary infection may result from9 its lack of tolerance. The symptoms shown may cause an error in diagnosis, so that treatment may be directed toward bacteria which could be the result of a susceptibility caused by a primary virus infection.
A:Some plant diseases may be caused by bacteria. B:Some plant diseases may be caused by pathogens. C:Some plant diseases may be caused by fungus. D:Symptoms are always helpful in identifying diseases.
?
?下面有3篇短文，每篇短文后有5道题，每题后面有4个选项。请仔细阅读短文并根据短文回答其后面的问题，从4个选项中选择1个最佳答案。
{{B}}第一篇{{/B}}
| {{B}}? ? ? ? ? ? ?
? ? ? ? ? ? ? ? ? ? Diseases
of Agricultural Plants{{/B}} ? ?Plants, like animals, are subject to diseases of various kinds. It has been estimated that some 30,000 different diseases attack our economic plants; forty are known to attack com, and about as many attack wheat. The results of unchecked plant disease are all too obvious in countries which have marginal food supplies. The problem will soon be more widespread as the population of the world increases at its frightening rate. Even in countries which are now amply fed by their agricultural products there could soon be critical food shortages. ?It is easy to imagine the consequences of some disastrous attack on one of the major crops; the resulting famines could kill millions of people, and the resulting hardship on other millions could cause political upheavals disastrous to the order of the world. ? ?Some plants have relative immunity to a great many diseases, while others have a susceptibility to them. The tolerance of a particular plant changes as the growing conditions change. A blight may be but a local infection easily controlled; on the other hand it can attack particular plants in a whole region or nation. An example is the blight which killed virtually every chestnut tree in North America. Another is the famous potato blight in Ireland in the last century. As a result of that, it was estimated that one million people died of starvation and related ailments. ? ?Plant pathologists have made remarkable strides in identifying the pathogens of the various diseases. Bacteria may invade a plant through an infestation of insect parasites carrying the pathogen. A plant can also be inoculated by man. Other diseases might be caused by fungus which attacks the plant in the form of a mold or smut or rust. Frequently such a primary infection8 will weaken the plant so that a secondary infection may result from9 its lack of tolerance. The symptoms shown may cause an error in diagnosis, so that treatment may be directed toward bacteria which could be the result of a susceptibility caused by a primary virus infection. |
A:Some plant diseases may be caused by bacteria. B:Some plant diseases may be caused by pathogens. C:Some plant diseases may be caused by fungus. D:Symptoms are always helpful in identifying diseases.
?
?下面有3篇短文，每篇短文后有5道题，每道题后面有4个选项。请仔细阅读短文并根据短文内容回答其后面的问题，从4个选项中选择1个最佳答案。
{{B}}第一篇{{/B}}
| {{B}}? ? ? ? ? ? ?
? ? ? ? ? ? ? ? ?Diseases of
Agricultural Plants{{/B}} ? ?Plants, like animals, are subject to diseases of various kinds. It has been estimated that some 30,000 different diseases attack our economic plants; forty are known to attack com, and about as many attack wheat. The results of unchecked plant diseases are ail too obvious in countries that have marginal food supplies. The problem will soon be more widespread as the population of the world increases at its frightening rate. Even in countries that are now amply fed by thek agricultural products there could soon be food shortages. It is easy to imagine the consequences of some disastrous attack on one of the major crops; the resulting famines could kill millions of people, and the resulting hardship on other millions could cause political upheavals disastrous to the order of the world. ? ?Some plants have relative immunity to great many diseases, while others have a susceptibility to them. The tolerance of a particular plant changes as the growing conditions change. A blight may be but a local infection easily controlled; on the other hand it can attack particular plants in a whole region or nation. An example is the blight that killed virtually every chestnut tree in North America. Another is the famous potato blight in Ireland in the last century. As a result of that, it was estimated that one million people died of starvation and related ailments. ? ?Plant pathologists have made remarkable strides in identifying the pathogens of the various diseases. Bacteria may include invade a plant through an infestation of insect parasites carrying the pathogen. A plant can also be inoculated by man. Other diseases might be caused by fungus which attacks the plant in the form of a mold or smut or rust. Frequently such a primary infection will weaken the plant so that a secondary infection may result from its lack of tolerance. The symptoms shown may cause an error in diagnosis, so that treatment may be directed toward bacteria which could be the result of a susceptibility caused by primary virus infection. |
A:Some plant diseases may be caused by bacteria. B:Some plant diseases may be caused by pathogens. C:Some plant diseases may be caused by fungus. D:Symptoms are always helpful in identifying diseases.
{{B}}第二篇{{/B}}
| ? ? ?The genes that help determine a
person’s individual characteristics—from the color of his eyes to the score he
makes on an IQ test—are located on chromosomes within the cells of his body.
Half of a person’s chromosomes come from his father, half from his mother. Many
diseases are the result of a single defective gene on one of the chromosomes.
Achondroplastic dwarfism, for example, is caused by a dominant gene and any
child who inherits it will have the disease. A genetic counselor confronted by a
parent with such a disease could warn that half of his children risk the
disease. More often, genetic diseases are caused by recessive genes. The most
common is cystic fibrosis, a disorder that affects at least one in every 1600
babies and causes their lungs and other body organs to become congested with
mucus. Some diseases, such as the blood-clotting disorder, hemophilia, are
sex-linked recessive defects carried on the female X chromosome. ? ? ?Many genetic defects, such as the hemophilia of European royalty, can be traced back through the family tree. And a genetic counselor can calculate probable risks for couples even before they have defective children. But faulty genes may also occur without warning by mutation in any generation. ? ? ?In recent years, researchers have detected a number of disorders caused by an extra chromosome, or lack of part of a chromosome. Mongolism, a form of retardation accompanied by short stature, a flattened nose and broad hands and feet, is caused by an extra chromosome. The parents of such a child have little increased risk of having another Mongoloid. ? ? ?There are blood, urine and other tests which show promise in detecting more than 100 genetic diseases, including cystic fibrosis, hemophilia and some forms of muscular dystrophy. ? ? ?Researchers are also detecting genetic defects even before a child is born. "Intrauterine detection," notes Dr. Henry L. Nadler of Northwestern University Medical School, "brings a new dimension to genetic counseling. The physician may now inform the parents that they will have either an affected or a normal child. " |
A:Some diseases result from an extra chromosome. B:Some diseases are caused by a chromosome in short. C:Faulty genes caused by mutation give rise to diseases like mongolism. D:Parents of mongoloid are likely to have more children of the kind.
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