Miguel quería inscribirse en el curso del mes que viene.（）

听力原文：Welcome to our series on renewable resources. The topic today is hydropower. As you most probably know, 'hydro' means water—so we are talking about using water to generate electricity. Of course, there are many ways to generate electricity but hydropower is important to the community, firstly and obviously, because it's renewable. The earth's hydrologic cycle of constant evaporation and transpiration provides a continual supply of water from rainfall and snowmelt. The second point to consider is its efficiency. Hydropower plants are able to convert approximately 90% of the energy from the falling water into electric energy whereas many fossil-fuelled plants lose more than half of the energy content of their fuel by way of waste heat and gases. For this reason they are very efficient.

Hydropower is also clean. It doesn't emit harmful gases that contribute to air pollution, acid rain, and global warming. No trucks, trains or pipelines are needed to bring fuel to the site and there's no noise pollution either. Furthermore, hydropower plant machinery is fairly simple and runs at slow speeds, which makes it reliable and durable. And, hydropower units are flexible also—they have the ability to start quickly and adjust rapidly to changes in demand for electricity, thus enabling them to meet peak loads. But this also allows them to serve as reserve capacity and bring more stability to the power system overall.

The dams that provide hydroelectric power also have other uses such as navigation, flood damage reduction, water supply, recreation, irrigation and low flow augmentation but it's not the purpose of this talk to go into those details.

How do the hydropower plants work? Well, a dam is built across a river which captures water to form. a reservoir and raises the water level to create 'head'. Think of 'head' as the vertical distance that the water falls as it passes through the dam, in other words, the difference in water level between the reservoir behind the dam and the river below. Water from the reservoir flows through an intake gate into a penstock—this is kind of a narrow channel which leads to the turbine below. The force of the water causes the turbine to rotate rapidly which, in turn, drives the generator to spin and produce electricity. The electricity is carried the long distances from the powerhouse to substations on the outskirts of cities via power lines.

Can you build a hydropower unit on any river? Well, no, just having water in a river isn't enough. A good dam site must have enough stream flow as well as enough head. A fast flowing river on the plains is probably not suitable because a dam couldn't be built high enough to provide the head needed for efficient production of electricity. On the other hand, dams in arid high country may have plenty of head but insufficient stream flow. The perfect spot for a hydropower plant is where the right combination of stream flow and head exists.

What about the environment? Surely the construction of large dams has an environmental impact? Well, yes it does. Certainly dams and reservoirs are built to improve the lives of people living in towns, farming communities and cities. But there must be a balance between development and preserving the natural environment. Needless to say, the natural river environment is changed which leads to changes in river ecology and aquatic habitat. Sometimes, for example, dissolved oxygen levels below dams get so low in summer that there is a negative impact on aquatic life. These levels can be improved, however, by using special aerating turbines and/or injecting oxygen directly into the stream flow. In order to protect and improve the habitat for endangered and other species of birds, fish and water life, there needs to be a thorough review of operating plans to see if a better balance can be achieved.

Hydropower plant design and operation must not only meet the needs of consumers for electricity but work hand-in-hand with agencies whose concern is for the fish and wildlife, water quality and water supply.

Complete the notes below.

Write ONE WORD ONLY for each answer.

Hydropower

Renewable—constant source (31) from natural hydrologic cyde

(32) —90% of hydro energy→electricity

Clean—no air or (33) pollution

(34) & curable—simple to operate

Flexible—can startadapt quickly to meet demand→leads to (35) of power supply.

(31)

Because of the complexity of the modern machine, most offices require secretaries ______.

A．to have specified training

B．specified in training

C．to train specifiedly

D．training specified

Because of the complexity of the modern machine, most offices require secretaries ________.

A．to have specified training

B．specified in traing

C．to train specifiedly

D．training specified

In a natural disaster -- a hurricane, flood, tornado, volcanic eruption, or other calamity -- minutes and even seconds of warning can be the difference between life and death. Because of this, scientists and government officials are working to use the latest technological advances to predict when and where disasters will happen. They are also studying how best to analyze and communicate this information once it is obtained. The goal is to put technology to effective use in saving lives and property when nature unleashes its power with devastating results.

On September 29, 1998, Hurricane Georges made landfall in Biloxi, Mississippi, after devastating Haiti, the Dominican Republic, Puerto Rico, and several islands of the Caribbean with torrential rains and winds up to 160 km/h (100 mph). Few people lost

their lives along the Gulf Coast of the United States, although hundreds died in the Caribbean.

This was a very different outcome from 1900, when a powerful Gulf Coast hurricane made an unexpected direct hit on Galveston, Texas, killing at least 6,000 people. Vastly improved hurricane warnings explain the different circumstances at either end of the 20th century residents of Galveston had no advance warning that a storm was approaching, while residents of Biloxi had been warned days in advance of Georges's approach, allowing for extensive safety precautions.

At the same time that people in Biloxi were thankful for the advance warning, some residents of New Orleans, Louisiana, 120 km (75 mi) to the west, were less satisfied. A day before Georges made landfall, forecasters were predicting that the hurricane had a good chance of striking New Orleans. Because much of New Orleans lies below sea level, the city is at risk for flooding. In addition, because New Orleans has a large population in vulnerable locations, emergency management officials must begin evacuations well before a storm strikes. But evacuation costs money: businesses close, tourists leave, and citizens take precautionary measures. The mayor of New Orleans estimated that his city's preparations for Georges cost more than $ 50 million. After the full fury of Georges missed New Orleans, some residents questioned the value of the hurricane forecasts in the face of such high costs.

The differing views on the early warnings for Hurricane Georges illustrate some of the complexities involved in predicting disasters. Disaster prediction is more than just forecasting the future with advanced technology it is also a process of providing scientific information to the government officials and other decision makers who must respond to those predictions.

In general, the process has three phases. First, there is the challenge of forecasting the event itself. In the case of Georges, scientists worked to predict the future direction and strength of the hurricane days in advance.

A second important challenge is communicating the forecast to decision makers. Because forecasts are always uncertain, a central factor in disaster predictions is communicating this uncertainty. Uncertainty is usually described in terms of odds or probabilities, much like daily weather forecasts. The media plays an important role in communicating predictions and their uncertainty to the public.

The third part of the process is the use of predictive information by decision makers. Even the most accurate information is of little value if the decision maker does not use it appropriately, for example in deciding whether to order an evacuation. If there is a breakdown in any of these three phases of prediction, the result is increased danger and a higher risk of loss of life.

According to the passage, the purpose of disaster prediction is to

A．demonstrate the power of advanced technology.

B．bring out the truth between life and death.

C．prevent such natural disasters from happening.

D．reduce human casualties and loss of property.

第三篇 Smart Exercise

Doctors are starting to find more and more information that suggests a connection between exercise and brain development. Judy Cameron, a scientist at Oregon Health and Science University, studies brain development. According to her research, it seems that exercise can make blood vessels, including those in the brain, stronger and more fully developed. Dr. Cameron claims this allows people who exercise to concentrate better. As she says: "While we already know that exercise is good for the heart, exercise can literally cause physical changes in the brain."

The effects of exercise on brain development can even be seen in babies. Babies

who do activities that require a lot of movement and physical activity show greater brain development than babies who are less physically active. With babies, even a little movement can show big results. Margaret Barnes, a pediatrician (儿科医师)， believes in the importance of exercise. She thinks that many learning disabilities that children have in elementary school or high school can be traced back to a lack of movement as babies. "Babies need movement that stimulates their five senses. They need to establish a connection between motion and memory. In this way, as they get older, children will begin to associate physical activity with higher learning," says Margaret.

Older people can beef up their brains as well. Cornell University studied a group of seniors ranging in age from seventy to seventy-nine. Their study showed a short-term memory increase of up to 40 percent after exercising just three hours a week. The exercise does not have to be very difficult, but it does have to increase the heart rate. Also, just like the motion for infants, exercise for older people should involve some complexity. Learning some new skills or motions helps to open up memory paths in the brain that may not have been used for a long time.

For most people, any type of physical activity that increases the heart rate is helpful. The main goal is to increase the brain's flow of blood. And your brain can benefit from as little as two to three hours of exercise a week.

第 40 题 Research by Dr. Cameron seems to suggest that exercise can

A．generate new blood vessels,

B．change the way a person thinks.

C．promote brain development.

D．divert one's attention,