Scientists have established that influenza viruses taken from man can cause the disease in animals. In addition, man can catch the disease from animals. In fact, a great number of wild birds seem to carry the virus without showing an evidence of illness. Some scientists concluded that a large family of influenza viruses may have evolved in the bird kingdom, a group that has been on the earth 100 million years and is able to carry the virus without contracting the disease. There is even convincing evidence to show that virus strains are transmitted from place to place and from continent to continent by migrating birds.

A . succeed B . proceed C . exceed D . exce

A . Small sips at regular intervals during the day B . The complete daily ration at one time during the day C . One-third the daily ration three times daily D . Small sips only after sunset

A、active B、resistant C、tough D、gradual

A . 10 B . 20 C . 30 D . 40

A．steadily and more effectively B．faster and more efficiently C．more powerfully D．more effectively

Sharks do not have bones, and a shark has an extremely good sense of smell. It can find. small amounts of substances in the water, such as blood, body liquids and chemicals produced by animals. Sharks also sense electrical and magnetic power linked to nerves and muscles of living animals. These powerful senses help them find their fond. Some sharks will eat just about anything. Many unusual things have been found in the stomachs of some large sharks. They include shoes, dogs, a cow's foot and metal protective clothing. About forty percent of the different kinds of sharks lay eggs. The others give birth to live young. Some sharks carry their young inside their bodies like humans do. Scientists are beginning to understand the importance of sharks to humans. Medical researchers want to learn more about the shark's body defense system against disease. They know that sharks recover quickly from injuries. Sharks appear never to suffer infections, cancer or heart diseases. What is this passage mainly about？ A．The necessity of protecting sharks. B．The living environment of sharks. C．The dangers of sharks to human beings. D．An introduction to sharks.

Scientists have discovered a genetic defect that appears to cause deficit-hyperactivity disorder, more commonly known as hyperactivity. People afflicted with this disorder have trouble focusing their attention and controlling impulses, and tend to be rest-less and aggressive. The defect occurs in a gene that regulates the body's use of the thyroid hormone. This finding was made in continuing study organized by the National Institute of Diabetes and Digestive and Kidney Diseases in which 70 percent of children inheriting the gene were hyperactive while only 20 percent of the children not inheriting the gene were hyperactive. And although the researchers admit that this defective gene probably accounts for only a fraction of cases of hyperactivity, this discovery will allow doctors to spot newborn babies likely to have the disorder, and also to provide clues for its cause and treatment.

A．action B．connection C．union D．function

A．the nucleus of a cell B．cloned human beings C．a human being in two years D．a law to ban human cloning E．a report on hunman cloning F．heavy media coverage

A．Y B．N C．NG

More than 60 people died in this earthquake. By comparison, an earthquake of similar intensity that shook America in 1988 claimed 25, 000 victims. Injuries and deaths were relatively less in Los Angeles because the quake occurred at 4:31 a.m. on a holiday, when traffic was light on the city's highways. In addition, changes made to the construction codes in Los Angeles during the last 20 years have strengthened the city's buildings and highways, making them more resistant to quakes. Despite the good news, civil engineers aren't resting on their successes. Pinned to their drawing boards are blueprints for improved quake-resistant buildings. The new designs should offer even greater security to cities where earthquakes often take place. In the past, making structures quake-resistant meant firm yet flexible materials, such as steel and wood, that bend without breaking. Later, people tried to lift a building off its foundation, and insert rubber and steel between the building and its foundation to reduce the impact of ground vibrations. The most recent designs give buildings brains as well as concrete and steel supports, called smart buildings. The structures respond like living organisms to an earthquake's vibrations. When the ground shakes and the building tips forward, the computer would force the building to shift in the opposite direction. The new smart structures could be very expensive to build. However, they would save many lives and would be less likely to be damaged during earthquakes. One reason why the loss of lives in the Los Angeles earthquake was comparatively low is that ______. A．new computers had been installed in the buildings B．it occurred in the residential areas rather than on the highways C．large numbers of Los Angeles residents had gone for a holiday D．improvements had been made in the construction of buildings and highways

A．Honeybees are flying all across the country. B．25-40 percent of the honeybees in the US have died. C．Honeybees are leaving their hives and do not return. D．Honeybee hives are in disorder．

A．solving B．exploring C．settling D．handling

A．whom B．with whom C．which D．with which