单选题The police chief argued that first-time offenders who have no high school diploma but who have families with a record of crime will probably break the law again.A who have no high school diploma but who have families with a record of crimeB without a h

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Dangers Await Babies with Altitude
Women who live in the world's highest communities tend to give birth to underweight babies, a new study suggests.These babies may grow into adults with a high risk of heart disease and strokes.
Research has hinted that newborns in mountain communities are lighter than average.But it wasn't clear whether this is due to reduced oxygen levels at high altitude or because their mothers are under-nourished—many people who live at high altitudes are relatively poor compared with those living lower down.
To find out more,Dino Giussani and his team at Cambridge University studied the records of 400 births in Bolivia during 1997 and 1998 .The babies were born in both rich and poor areas of two cities:La Paz and Santa Cruz.La Paz is the highest city in the world,at 3 .65 kilometers above sea level,while Santa Cruz is much lower,at 0 .44 kilometers.
Sure enough,Giussani found that the average birthweight of babies in La Paz was significantly lower than in Santa Cruz.This was true in both high and low-income families.Even babies born to poor families in Santa Cruz were heavier on average than babies born to wealthy families in lofty La Paz.“We were very surprised by this result,”says Giussani.
The results suggest that babies born at high altitude are deprived of oxygen before birth.
“This may trigger the release or suppression of hormones that regulate growth of the unborn child,”says Giussani.
His team also found that high-altitude babies tended to have relatively larger heads compared with their bodies.This is probably because a fetus starved of oxygen will send oxygenated blood to the brain in preference to the rest of the body.
Giussani wants to find out if such babies have a higher risk of disease in later life.People born in La Paz might be prone to heart trouble in adulthood,for example.Low birthweight is a risk factor for coronary heart disease.And newborns with a high ratio of head size to body weight are often predisposed to high blood pressure and strokes in later life.

It can be learned from the last paragraph that______.
A: high-altitude babies tend to have high blood pressure in their later life
B: underweight babies have a shorter life span
C: babies born to poor families lack certain hormones before birth
D: newborns in wealthy families have larger heads compared with their bodies

A new scheme for getting children to and from school is being started by the education authorities in part of Eastern England． This could end the worries of many parents fearful for their children's safety on the roads．
Until now the Country Council has only been prepared to provide bus services for children living more than three miles from their school, or sometimes less if special reasons existed． Now it has been decided that if a group of parents ask for help in organizing transport they will be prepared to go ahead, provided the arrangement will not lose money and that children taking part will be attending their nearest school．
The new scheme is to be tried out this term for children living at Milton who attend Impington school． The children live just within the three-mile limit and the Council has said in the past it will not undertake to provide free transport to the school． But now they have agreed to organize a bus service from Milton to Impington and back, a plan which has the support of the school's headmaster．
Between 50 and 60 parents have said they would like their children to take part in． Final calculations have still to be carried out, but a council official has said the cost of parents should be less than $6．50 a tenn．
They have been able to arrange the service at a low cost because there is already an agreement with the bus company for a bus to take children who live further away to Impington． The same bus would now just make an extra journey to pick up the Milton children． The official said they would get in touch with other groups of parents who in the past had asked if transport could be provided for their children, to see if they would like to take part in the new scheme．
The children the Council ran buses for in the past were those__________．

A.whose parents were worried about them
B.who would have had to walk otherwise
C.who could not walk
D.who had to travel a long way

Today ,as in every other day of the year ,more than 3000 U.S. adlescents will smoke their first cigarette on their way to becoming regular smokers as adults. During their lifetime,it can be expected that of these 3000 about 23 will be murdered,30 will die in traffic accidents, and nearly 750 will be killed by a smoking-related disease. The number of deaths attributed to cigarette smoking outweithts all other factors, whether voluntary or involuntary, as a cause of death.
Since the late 1970s, when daily smoking among high school seniors reached 30 precent , smoking rates among youth have declined . While the decline is impressive ,several important issues must be raised.
First, in the past several years,smoking rates among youth have declined very little. Second,in the late 1970s ,smoking among male high school seniors exceeded that among female by nearly 10 percent . The statistic is reversing.Third ,several recent studies have indicate high school dropouts have excessively high smoking rates, as much as 75 percent .
Finally, thouth significant declines in adolescent smoking have occurred in the past decade,no definite reasons for the decline exist. Within this context,the Naional Cancer Instiute (NCI) began its current effort to determine the most effecive measures to reduce smoking levesl among youth.
By "dropout" the author means___.

a.students who failed the examination
b.students who left school
c.students who lost their way
d.students who were driven out of school