相关试题
A peculiarly pointed chin is his most memorable facial characteristic.
A:mark
B:feature
C:trace
D:appearance
Her speciality is heart surgery.
A:region
B:site
C:field
D:platform
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Food Fright
Experiments under way in several labs aim to create beneficial types of genetically modified(GM)foods,including starchier potatoes and caffeine-free coffee beans.Genetic engineers are even trying to transfer genes from a cold-water fish to make a frost-resistant tomato.A low-sugar GM strawberry now in the works might one day allow people with health problems such as diabetes to enjoy the little delicious red fruits again.GM beans and grains supercharged with protein might help people at risk of developing kwashiorkor. Kwashiorkor,a disease caused by severe lack of protein,is common in parts of the world where there are severe food shortages.
Commenting on GM foods,Jonathon Jones,a British researcher,said,"The future benefits will be enormous,and the best is yet to come."
To some people,GM foods are no different from unmodified foods."A tomato is a tomato," said Brian Sansoni,an American food manufacturer.
Critics of GM foods challenge Sansoni's opinion.They worry about the harm that GM crops might do to people,other animals,and plants.
In a recent lab study conducted at Cornell University,scientists tested pollen made by Bt corn,which makes up one-fourth of the U .S.corn crop.The scientist sprinkled the pollen onto milkweed,a plant that makes a milky juice and is the only known food source of the monarch but-terfly caterpillar. Within four days of munching on the milkweed leaves,almost half of a test group of caterpillars had died."Monarchs are considered to be a flagship species for conservation,"said Cornell researcher Linda Raynor."This is a warning bell."
Some insects that are not killed by GM foods might find themselves made stronger. How so? The insecticides used to protect most of today's crops are sprayed on the crops when needed and decay quickly in the environment.But GM plants produce a continuous level of insecticide.Insect species feeding on those crops may develop resistance to the plants and could do so in a hurry, say the critics.Insects may also develop a resistance to the insecticide Bt.
At the forum on GM food held last year in Canada,GM crops that have been made resistant to the herbicide might crossbreed with wild plants,creating"superweeds"that could take over whole fields.
So where do you stand?Should GM foods be banned in the United States,as they are in parts of Europe?Or do their benefits outweigh any of the risks they might carry?
What happens to those insects when not killed by the spray of insecticide?
A: They may lose their ability to produce offspring.
B: They may have a higher ability to adapt to the environment.
C: They move to other fields free from insecticide.
D: They never eat again those plants containing insecticide.
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ADHD Linked to Air Pollutants
Children have an increased of attention problems,seen as early as grade school,if their no-ses inhaled(吸入)a certain type of air pollution when they were pregnant. That's the finding of a new study.Released when things aren't burned completely,this pollution is known as polycyclic aromatic hydrocarbons,or PAHs.The biggest sources of these PAHs:the burning of fossil fuels, wood and trash.
Frederica Perera works at Columbia University's Mailman School of Public Health in New York City.She researches how exposure to things in the environment affects children's health.In a new study,she and her team studied the exposure to air pollution of 233 nonsmoking pregnant women in New York City. Because burning tobacco can spew(排放)PAHs into the air and lungs, Perera's team focused on nonsmokers. The researchers wanted to probe(探查)other sources of PAHs,ones that's would have been hard for an individual to avoid.
The team started by testing the blood of each woman during pregnancy.The reason:Any PAHs in a woman's blood would also be available to the baby in her womb.Nine years later,the researchers investigated signs of attention problems in those children,now age 9 .They asked each child's mother a series of questions.These included whatever her child had problems doing things that needed sustained(长期的)mental effort, such as homework or games with friends. The sci-entists also asked if the kids had trouble following instructions or made frequent,careless mis-takes .All of these can be symptoms of a disorder called Attention Deficit Hyperactivity Disorder, or ADHD.About one in U.S.children has ADHD.
Among the women studied,traffic and home heating were the primary sources of air pollution exposure,Perera and her team suspect. Some of these women had low levels of PAHs in their blood .Others had high levels.Those with high levels were five times as likely to have children who showed attention problems by age 9 .The new findings were published November 5 in the journal PLOS ONE.
The main purpose of the research was to find out how exposure to PAHs played a role in har-ming the subjects' physical health.
A:Right
B: Wrong
C:Not mentioned
_____
A.For example, the people in men's dreams are often other men, and the dreams often involve fighting.
B.Men and women dream about different things.
C.A criminal, for example, might dream about crime.
D.However, one thing they agree on this: If you dream that something terrible is going to occur, you shouldn't panic.
E.It was only in the twentieth century that people started to study dreams in a scientific way.
F.He thought people could learn more about themselves by thinking about their dreams.