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.
It’s known that two influenza viruses can recombine when both are present in an animal at the same time, the result of such recombination is a great variety of strains containing different H and N spikes. This raises the possibility that a human influenza virus can recombine with an influenza virus from a low animal to produce an entirely new s
A. H and N spikes are produced
B. animal and bird viruses are combined
C. dissimilar types of viruses recombine
D. two viruses of the same type are contracted
Passage Five
Scientists claim that air pollution causes a decline in the world’ s average air temperature. In order to prove that theory, ecologists have turned to historical data in relation to especially huge volcanic eruptions. They suspect that volcanoes effect weather changes that are similar to air pollution.
One source of information is the effect of the eruption of Tambora, a volcano in Sumbawa, the Dutch East Indies ( the former name of the Republic of Indonesia) ,in April 1815. The largest recorded volcanic eruption, Tambora threw 150 million ton of fine ash into the stratosphere. The ash from a volcano spreads worldwide in a few days and remains in the air for years. Its effect is to turn in coming solar radiation into space and thus cool the earth. For example, records of weather in Eng land show that between April and November 1815, the average temperature had fallen 4.5°F during the next twenty-four months, England suffered one of th
A. England' s proximity to the North Sea
B. Volcanic ash in the atmosphere
C. Floorings in the area
D. Pollution caused by the International Revolution
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