题目内容
Part A
Directions: Read the following texts and answer the questions which accompany them by choosing A, B, C or D. Mark your answers on ANSWER SHEET 1.
In recent years, there has been a steady assault on salt from the doctors: Salt is bad for you—regardless of your health. Politicians also got on board. "There is a direct relationship, " US congressman Neal Smith noted, "between the amount of sodium a person consumes and heart disease, circulatory disorders, stroke and even early death. "
Frightening, if true! But many doctors and medical researchers are now beginning to feel the salt scare has gone too far. "All this hue and cry about eating salt is unnecessary, " Dr. Dustan insists. "For most of us it probably doesn't make much difference how much salt we eat. " Dustan's most recent short-term study of 150 people showed that those with normal blood pressure underwent no change at all when placed on an extremely low-salt diet, or later when salt was reintroduced. Of the hypertensive subjects, however, half of those on the low-salt diet did experience a drop in blood pressure, which returned to its previous level when salt was reintroduced.
"An adequate to somewhat excessive salt intake has probably saved many more lives than it has cost in the general population, "notes Dr. John H. Laragh. "So a recommendation that the whole population should avoid salt makes no sense. "
Medical experts agree that everyone should practice reasonable "moderation" in salt consumption. For an average person, a moderate amount might run from four to ten grams a day, or roughly 1/2 to 1/3 of a teaspoon. The e-quivalent of one to two grams of this salt allowance would come from the natural sodium in food. The rest would be added in processing, preparation or at the table.
Those with kidney, liver or heart problems may have to limit dietary salt, if their doctor advises. But even the very vocal "low salt" exponent, Dr. Arthur Hull Hayes, Jr. admits that "We do not know whether increased sodium consumption causes hypertension. " In fact, there is increasing scientific evidence that other factors may be involved: deficiencies in calcium, potassium, perhaps magnesium; obesity(much more dangerous than sodium); genetic predis-potition; stress.
"It is not your enemy, " says Dr. Laragh, "Salt is the No. 1 natural component of all human tissue, and the idea that you don't need it is wrong. Unless your doctor has proven that you have a salt-related health problem, there is no reason to give it up. "
According to some doctors and politicians, the amount of salt consumed______.
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Part C
Directions: Answer questions 71-80 by referring to the following games.
Note: Answer each question by choosing A, B or C and mark it on ANSWER SHEET 1. Some choices may be required more than once.
A = Hydro power B = Nuclear power C = Solar power D = Wind power Which power(power' s)...
was developed to provide electricity for satellites at the beginning？ 71.______
can promote tourism development？ 72.______
may give off dangerous radioactive pollution into the air？ 73.______
may affect the downstream water quality and have an impact on plant life？ 74.______
stations can increase to full power very quickly？ 75.______
produces small amounts of waste？ 76.______
is a good method of supplying energy to remote areas？ 77.______
provides around 20% of the world's electricity？ 78.______
can be used to heat your water at home instead of so much gas or electricity？ 79.______
is not renewable？ 80.______
A
Hydro power
Introduction
We have used running water as an energy source for thousands of years, mainly to grind corn.
The first house in the world to be lit by hydroelectricity was Cragside House, in Northumberland, England, in 1878. In 1882 on the Fox River, in the USA, hydroelectricity produced enough power to light two paper mills and a house.
Nowadays there are many hydro-electric power stations, providing around 20% of the world' s electricity. The name comes from "hydro" , the Greek word for water.
How it works
A dam is built to trap water, usually in a valley where there is an existing lake.
Water is allowed to flow through tunnels in the dam, to turn turbines and thus drive generators.
Advantages
Once the dam is built, the energy is virtually free.
No waste or pollution produced.
Much more reliable than wind, solar or wave power.
Water can be stored above the dam ready to cope with peaks in demand.
Hydro-electric power stations can increase to full power very quickly, unlike other power stations.
Disadvantages
The dams are very expensive to build.
Building a large dam will flood a very large area upstream, causing problems for animals that used to live there.
Finding a suitable site can be difficult—the impact on residents and the environment may be unacceptable.
Water quality and quantity downstream can be affected, which can have an impact on plant life.
Is it renewable？
Hydro-electric power is renewable.
The Sun provides the water by evaporation from the sea, and will keep on doing so.
B
Nuclear power
Introduction
Nuclear power is generated using Uranium, which is a metal mined in various parts of the world.
The first large-scale nuclear power station opened at Calder Hall in Cambria, England, in 1956.
Some military ships and submarines have nuclear power plants for engines.
How it works
Nuclear power stations work in pretty much the same way as fossil fuel-burning stations, except that a " chain reaction" inside a nuclear reactor makes the heat instead.
The reactor uses Uranium rods as fuel, and the heat is generated by nuclear fission. Neutrons smash into the nucleus
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