Passage Three Until two years ago, Clearing, Illinois was a tranquil suburb of Chicago. But residents grew alarmed when they noticed armed teenagers on the streets, giving gang signals and shouting at passing cars. Then came a series of burglaries and graffiti messages on store- fronts. By the time local authorities realized they had a gang problem, it was too late. Last December, two 13-year-old girls were shot outside their school as they sat in a car with two members of a local gang, the Ridgeway Lords. Nearly all 50 states have recently passed laws that allow youths aged 14-17 to be tried in court as adults. In about 25 states they have passed laws to punish parents for their children’s behavior. And in 146 of the nation’s largest cities, they have imposed curfews to reduce juvenile violence. When you look at the spectacular rise of violent crime among young people recently, it’s easy to understand the concern. Over the past decade, there ha
A. A famous band.
B. A gang.
C. A prison.
D. A unit.
Three years ago, researchers announced the discovery
of human genes that were capable of turning ordinary cells into malignant ones.
The news met with some skepticism. Experts asked how a single gene could cause
such a dramatic change. Why does cancer take years or even decades to develop if
it is caused by such a simple and direct process In last week’s issue of the,
three research teams answered those questions by setting forth a new model for
understanding the role of oncogenes in cancer. Each group found that it does in fact take more than a single gene to produce cancer in normal cells. Teams at M. I. T and Cold Spring Harbor Laboratory on Long Island, N. Y. , reported that they could induce cancer in normal rat cells only by inserting at least two types of oncogene into the cells. "A single oncogene produced some changes, A. was caused by normal cells B. sometimes resulted from internal actions of the victim’s own body C. was a hereditary disease D. was a form of malignancy [单项选择]Not until three years ago ______ to work outside.
A. he began B. he begins C. began he D. did he begin [填空题]Until about two million years ago, Africa’s vegetation had always been controlled by the interactions of climate; geology, soil, and groundwater conditions; and the activities of animals. The addition of humans to the latter group, however, has increasingly rendered unreal the concept of a fully developed "natural" vegetation—i.e., one approximating the ideal of a vegetational climax.
(16) Early attempts at mapping and classifying Africa’s vegetation stressed this relationship. sometimes the names of plant zones were derived directly from climates. In this discussion the idea of zones is retained only in a broad descriptive sense. (17) In addition, over time more floral regions of varying shape and size have been recognized. Many schemes have arisen successively, all of which have had to take views on two important aspects, the general scale of treatment to be adopted, and the degree to which human modification is to be comprehended or [填空题]
Until about two million years ago Africa’s vegetation had always been controlled by the interactions of climate; geology, soil, and groundwater conditions; and the activities of animals. The addition of humans to the latter group, however, has increasingly rendered unreal the concept of a fully developed "natural" vegetation-- i. e. , one approximating the ideal of a vegetational climax. (41) _____________________. Early attempts at mapping and classifying Africa’s vegetation stressed this relationship: sometimes the names of plant zones were derived directly from climates. In this discussion the idea of zones is retained only in a broad descriptive sense.
(42) _____________________. In addition, over time more floral regions of varying shape and size have been recognized. Many schemes have arisen successively, all of which have had to take views on two important aspects: the general scale of treatment to be adopted, and the degree to which human [单项选择]Passage Three
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