题目内容
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Vessels transiting the Canal must have their gangways and derricks ________
A.readjusted
B.removed
C.lowered
D.rigged in
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A.arteries
B.veins
C.venules
D.capillaries
Losing your ability to think and remember is prettyscary. We know the risk of dementia (痴呆症) increases with age. But if you have memory slips, you probably needn't worry. There are pretty clear differences between signs of dementia andage-related memory loss. After age 50, it's quite common to have trouble remembering the names of people, places andthings quickly, says Dr. Kirk Daffner of Brigham and Women's Hospital in Boston. The brain ages just like the rest of the body. Certain parts shrink, especially areas in the brainthat are important to learning, memory and planning. Changes in brain cells can affectcommunication between different regions of the brain. And blood flow can be reduced asblood vessels narrow. Forgetting the name of an actor in a favorite movie, for example, is nothing to worry about. Butif you forget the plot of the movie or don't remember even seeing it, that's far moreconcerning, Daffner says. When you forget entire experiences, he says, that's "a red flag that something more seriousmay be involved." Forgetting how to operate a familiar object like a microwave oven, orforgetting how to drive to the house of a friend you've visited many times before can also besigns of something going wrong. But even then, Daffner says, people shouldn't panic. There are many things that can causeconfusion and memory loss, including health problems like temporary stoppage of breathingduring sleep, high blood pressure, or depression, as well as medications (药物) likeantidepressants. You don't have to figure this out on your own. Daffner suggests going to your doctor to checkon medications, health problems and other issues that could be affecting memory. And the bestdefense against memory loss is to try to prevent it by building up your brain's cognitive (认知的) reserve, Daffner says. "Read books, go to movies, take on new hobbies or activities that force one to think in novelways," he says. In other words, keep your brain busy and working. And also get physicallyactive, because exercise is a known brain booster.Why does the author say that one needn't be concerned about memory slips？ 1..Why does the author say that one needn't be concerned about memory slips？()
A、Not all of them are symptoms of dementia.
B、They occur only among certain groups of people.
C、Not all of them are related to one's age.
D、They are quite common among fifty-year-olds.
Vessels required to be equipped with an approved backfire flame arrester are ______．
A.Those with diesel engines
B.All those with gasoline engines
C.Those with large engines only
D.None of the above
A.hold
B.holded
C.held
D.holding
A.Lubrication systems using engine driven lube oil pumps do not require any additionalindependent arrangement when such arrangements have been proven reliable.
B.The use of engine driven pre-lube pumps is permitted on vessels with propulsionsystems developing less than 500 shaft horsepower.
C.When forced lubrication is used for propulsion engines , one independently drivenstandby pumps is to be provided in addition to the necessary pumps for normaloperation.
D.Lubrication systems where two oil coolers are fitted require a minimum of twotemperature control devices which may be actuated by similar sensors.
A.the towing vessel should slip first
B.the vessel towed should slip first
C.they should slip simultaneously
D.either vessel may slip first
After age 50, it's quite common to have trouble remembering the names of people, places and things quickly, says Dr. Kirk Daffner of Brigham and Women's Hospital in Boston.
The brain ages just like the rest of the body. Certain parts shrink, especially areas in the brain that are important to learning, memory and planning. Changes in brain cells can affect communication between different regions of the brain. And blood flow can be reduced as blood vessels narrow.
Forgetting the name of an actor in a favorite movie, for example, is nothing to worry about. But if you forget the plot of the movie or don't remember even seeing it, that's far more concerning, Daffner says.
When you forget entire experiences, he says, that's "a red flag that something more serious may be involved." Forgetting how to operate a familiar object like a microwave oven, or forgetting how to drive to the house of a friend you've visited many times before can also be signs of something going wrong.
But even then, Daffner says, people shouldn't panic. There are many things that can cause confusion and memory loss, including health problems like temporary stoppage of breathing during sleep, high blood pressure, or depression, as well as medications (药物) like antidepressants.
You don't have to figure this out on your own. Daffner suggests going to your doctor to check on medications, health problems and other issues that could be affecting memory. And the best defense against memory loss is to try to prevent it by building up your brain's cognitive (认知的) reserve, Daffner says.
"Read books, go to movies, take on new hobbies or activities that force one to think in novel ways," he says. In other words, keep your brain busy and working. And also get physically active, because exercise is a known brain booster.
101.Why does the author say that one needn't be concerned about memory slips_____
A.Not all of them are symptoms of dementia.
B.They occur only among certain groups of people.
C.Not all of them are related to one's age.
D.They are quite common among fifty-year-olds.
102.What happens as we become aged according to the passage_____
A.Our interaction skills deteriorate.
B.Some parts of our brain stop functioning.
C.Communication within our brain weakens.
D.Our whole brain starts shrinking.
103.Which memory-related symptom should people take seriously_____
A.Totally forgetting how to do one's daily routines.
B.Inability to recall details of one's life experiences.
C.Failure to remember the names of movies or actors.
D.Occasionally confusing the addresses of one's friends.
104.What should people do when signs of serious memory loss show up_____
A.Check the brain's cognitive reserve.
B.Stop medications affecting memory.
C.Turn to a professional for assistance.
D.Exercise to improve their well-being.
105.What is Dr.Daffner's advice for combating memory loss_____
A.Having regular physical and mental checkups.
B.Taking medicine that helps boost one's brain.
C.Engaging in known memory repair activities.
D.Staying active both physically and mentally.
Prince Henry lived in the fifteenth century. As a boy he became devoted to the sea, and he dedicated (devoted) himself" to improving the design of Ships and the methods or sailing them. In 1416, when he was twenty-two. Henry founded a school for mariners, to which he invited everyone who could help him —— Jewish astronomers, Italian and Spanish sailors, and Arab mathematicians and map makers who knew how to use the crude compass of the day and could improve it.
Henry's goal was to design and equip vessels that would be capable of making long ocean voyages without having to hug (keep close to) the shore. The caravel carried more sail and was longer and slimmer than any ship then made, yet was tough enough to withstand gales at sea. He also developed the carrack, which was a slower ship, but one that was capable of carrying more cargo.
To Prince Henry the world owes credit far development of craft that made oceanic exploration possible. He lives in history as Henry the Navigator.
1.Prince Henry's principal achievement was that of ______
A、making oceanic exploration possible
B、improving the compass
C、founding a school for mariners
D、inventing the clipper ship
2.Prince Henry''s goal was to design vessels that could ______.
A、make long deep-sea voyages
B、travel faster than those in use at that time
C、explore the coastline of. Portugal
D、carry larger crews and more cargo than existing ones
3.Prince Henry started his school for the purpose of ______.
A、helping mariners
B、improving ship design and sailing methods
C、studying astronomy and mathematics
D、improving his own skill as a sailor
On earth gravity (引力) makes blood flow down towards the feet, so the heart must work to pump blood up. In space blood flows up towards the heart. The effect is similar to what happens when you lie with your feet up and your head down. The flowing blood is felt by receptors in the walls of arteries (动脉) in the upper part of the body and in the heart. These receptors send signals to the brain, but the brain reads them incorrectly. To the brain, the signals means the amount of blood in the body has increased, so the brain tells other parts of the body to react to the increase in the blood. For example, the body produces more urine (尿液), resulting in loss of body fluid and salt. At the same time the astronaut has less desire to drink and so does not replace the lost fluid.
As a spacecraft begins to fall back to earth atmosphere, the crew begins to feel gravity. Blood again flows towards the feet and collects there. The heart beats faster in an effort to pump enough blood to the brain. Some crew members may not get enough blood to the brain and the heart beats too fast. They become sick and even lose consciousness as their spacecraft reenters the earth atmosphere. To prevent this, special clothing is invited for astronauts to prevent blood collecting in their legs. They put it on just before the craft reenters the earth’s atmosphere. They also drink about a liter (升) of water and eat some salt to replace the fluid they have lost while in space.
Weightlessness affects the heart and blood vessels in another way. The heart does not work as hard in a weightless environment as it does in an environment of gravity. When the heart works less hard, the heart muscles become weaker. It is replaced by fibrous tissue and fat
41.If one lies with his feet up and his head down on earth, his()
A.blood will flow up towards the heart.
B.blood will flow down towards the feet.
C.heart will pump the blood up to the head.
D.heart will have to work harder.
42.What can we infer from the second paragraph of the passage()
A.The brain reads the signals incorrectly because it tends to go wrong in outer space
B.In space an astronaut should drink some water even when he does not feel thirsty.
C.In space the amount of water in the body of an astronaut increase.
D.The receptors in the walls of arteries often send wrong signals to the brain.
43.When the spacecraft reenters the earth’s atmosphere some astronauts become sick or even lose consciousness because()
A.their brains cannot get enough blood
B.their hearts are not strong enough
C.their blood collects in their feet
D.they begin to feel the gravity again
44.When the spacecraft enter the earth’s atmosphere, the astronauts should do the following except()
A.trying to regain their consciousness
B.eating some salt
C.drinking some water.
D.putting on special clothing
45.After a long time in space, an astronaut’s heart muscles become weaker because()
A.they are short of exercises when the heart works less hard.
B.the heart works too hard under an environment of weightlessness.
C.the astronaut’s hard work puts too great a burden on the heart.
D.they are completely replaced by fibrous tissue and fat.
A.y(t)=(e-t+e-2t)ε(t)
B.y(t)=(e-t)ε(t)
C.y(t)=(e-t–e-2t)ε(t)
D.y(t)=(–e-2t)ε(t)
