题目内容
| They ________ for hours, but neither of them would give in. A. discussed B. spoke C. argued D. talked
|
C
Attention deficit（不足）hyperactivity（活动过度）disorder is known by the letters A．D．H D．Children with A．D．H．D．might have trouble paying attention．They might not seem to listen and might forget things．They might not be able to stay seated or play quietly．They might talk too much and act and speak without thinking about the results of their behavior．These are among the signs named on the web site of America’s Centers for Disease Control and Prevention．
Doctors usually identify the disorder in children．But experts say the behaviors often last into adulthood．Researchers have been looking for the cause or causes of attention deficit hyperactivity disorder．Now, a brain-imaging study offers more evidence that could lead to new ways to treat it．Researchers say they observed shortages in the brain's reward system in patients with A．D．H．D．The study found that levels of some proteins were lower than normal．Nora Volkow, director of the National Institute on Drug Abuse, says the lack of attention and self –control that mark A.B.H.D. could be caused by problem in the flow of dopamine（多巴胺）. She says people might have difficulty completing an activity if they cannot expect some kind of reward in return. Researchers studied the pathways on which dopamine travels and A.D.H.D. Doctor Volkow says the researchers then compared the pathways to those of 44 adults without the disorder. “There was a lower concentration of dopamine markers in the brain of individuals with A.D.H.D., specifically in the areas of the brain that are involved with reward and motivation. And the dopamine levels were directly linked to the severity, of the patient’s inattention she says.”
The study used brain images taken at Brookhaven National Laboratory in new York State. Gene-Jack Wang is chairman of the Brookdhaven medical department. He says the finding might also help explain why people with A.D.H.D.
are more likely to abuse drugs or overeat. He says they might be attempting to increase their dopamine levels to make up for the deficits in their reward system.
| Title | ●The finding of |
| The of Children with A.D.H.D. | ●They are lacking in . ●Perhaps they don’t seem to listen. ●Perhaps they are . ●Perhaps they can’t sit for or play quietly. ●They might talk too much and act and speak without the results of their behavior |
| The of A.D.H.D. | ●patients with A.D.H.D are of the brain’s reward. ●Levels of some proteins are lower than normal. ●Levels of dopamine are as well. |
| Reasons of abusing Drugs | ●They are trying to their dopamine. |
ave been rising considerably.Today, bicycles are elegantly simple machines that are common around the world. Many people ride bicycles for recreation, whereas others use them as a means of transportation. The first bicycle was invented in Germany in 1818. Because it was made of wood, it wasn’t very strong nor did it have pedals (脚踏板）.Riders moved it by pushing their feet against the ground.
In 1839, Kirkpatrick Macmillan, a Scottish blacksmith, invented a much better bicycle. Macmillan’s machine had iron-covered wheels to keep them from getting worn down. He also used foot-operated levers, similar to pedals, so his bicycle could be ridden at a quick pace. It didn’t look much like the modem bicycle, though, because its back wheel was substantially larger than its front wheel. Although Macmillan’s bicycles could be ridden easily, they were never produced in large numbers.
In 1861, Frenchman Pierre Michaux and his brother Ernest invented a bicycle with an improved pedal mechanism. They called their bicycle a velocipede，but most people called it a “bone shaker” because of the effect of the wood and iron frame. Despite the impolite nickname, the velocipede was a hit. After a few years, the Michaux family was making hundreds of the machines annually, mostly for fun-seeking young people.
Ten years later, James Starley , an English inventor, made several innovations that revolutionized bicycle design. He made the front wheel many times larger than the back wheel, put a gear on the pedals to make the bicycle more efficient，and lightened the wheels by using wire spokes. Although this bicycle was much lighter and less tiring to ride, it was still clumsy, extremely top-heavy，and ridden mostly for entertainment.
It wasn’t until 1874 that the first truly modern bicycle appeared on the scene. Invented by another Englishman, H. J. Lawson, the safety bicycle would look familiar to today’s cyclists. The safety bicycle had equal-sized wheels, which made it easier to ride. Lawson also attached a chain to the pedals to drive the back wheel. By 1893，the safety bicycle had been further improved with air-filled rubber tires, a diamond-shaped frame, and easy braking. With the improvements provided by Lawson; bicycles became extremely popular and useful for transportation. Today, they are built, used, and enjoyed all over the world.
【小题1】This passage was most likely written in order to _____.
| A．compare bicycles used for different purposes |
| B．describe the problems early bicycle makers experienced |
| C．persuade readers to use bicycles for transportation |
| D．tell readers about the early history of the bicycle |
| A．add weight to the bicycle |
| B．make the bicycle easier to ride |
| C．allow the wheels to last longer |
| D．let the bicycle be more comfortable |
【小题4】Which of the following statements is true according to the passage?
| A．Two hundred years ago，bicycles did not exist. |
| B．The first bicycle could be ridden at a very quick pace. |
| C．The Michaux brothers called their bicycle a “bone shaker”. |
| D．Macmillan’s machine had wheels with rubber tires. |
| A．importance | B．time | C．place | D．Interest |