单选题 In 1957 a doctor in Singapore noticed that hospitals were treating an unusual number of influenza-like cases. Influenza is sometimes called "flu" or a "bad cold". He took samples from the throats of patients, and his hospital was able to find the virus of this influenza.
There are three main types of the influenza virus. The most important of these are Type A and B, each of them having several subgroups. With the instrument of the hospital the doctor recognized that the outbreak was due to a virus in Group A, but he did not know the subgroup. Then he reported the outbreak to the World Health Organization in Geneva. W. H. O. published the important news alongside reports of a similar outbreak in Hong Kong, where about 15%～20% of the population had become ill.
As soon as the London doctors received the package of throat samples, doctors began the standard tests. They found that by reproducing itself at very high speed, the virus had grown more than a milion times within two days. Continuing their careful tests, the doctors checked the effect of drugs against all the known subgroups of Type A virus. None of them gave any protection. This, then, was something new, a new influenza virus, against which the people of the world had no help whatever.
Having found the virus they were working with, the two doctors now dropped it into the noses of some specially selected animals, which got influenza as much as human being did. In a short time the usual signs of the disease appealed. These experiments proved that the new virus was easy to catch, but that it was not a killer. Scientists, like the general public, called it simply Asian Flu.
The first discovery of the virus, however, was made in China before the disease had appeared in other countries. Various reports showed that the influenza outbreak started in China, probably in February of 1957. By the middle of March it had spread all over China. The virus was found by Chinese doctors early in March. But China was not a member of the World Health Organization and therefore did not report outbreaks of the disease to it. Not until two months later, when travellers carried the virus into Hong Kong, from where it spread to Singapore, did the news of the outbreak reach the rest of the world. By this time, it was well started on its way around the world.
Thereafter, W. H. O.'s weekly reports described the steady spread of this great virus outbreak, which within four months swept through every continent.

单选题 The doctor in Singapore performed a valuable service by ______.
A. finding the subgroup of the virus B. developing a cure
C. keeping his patients apart from others D. reporting the outbreak to W. H. O.

单选题 One interesting thing about the virus in the story was that it ______.
A. was especially weak B. was similar to other viruses
C. could reproduce at great speed D. had samples frozen and packed in dry ice

单选题 The type of influenza discussed in this story ______.
A. had been classified years before B. could not be cured by any known drug
C. could be prevented from spreading D. could not affect adults

单选题 The experiments in giving the virus to animals proved that this type of influenza was easy to catch ______.
A. and could possibly cause death B. and had rather mild effects
C. but was not deadly D. and did not have the usual signs

单选题 One reason why the outbreak of the disease was not discovered sooner was that ______.
A. China did not belong to W. H. O. B. doctors in Asia did not recognize the disease
C. reporting procedures were not good enough D. the people who caught it were travellers