Question

The coldis the most common of man’s ailments(疾病). Yet it stumped(難住)the medical authorities. Many of more terrible diseases have comeunder the control of modem man as the result of the knowledge gained in the labof science research. Investigators have thought that the cold is usually causedby a virus(病毒). However, no method of studying this virus has been devised(提出). The chimpanzee(黑猩猩)is the only animal towhich the disease can be given experimentally. The use of this animal islimited by its cost and by the fact that so many of the animals die ofpneumonia during the experiments. This leaves for all practical purposes onlyhuman volunteers to be used in research projects. Many people of prisons havehelped in this work, but because of .these limitations, research into the causeand cure of colds has progressed very slowly.Research into the cause and cure of colds has________.

1. A.
   gone ahead very slowly
2. B.
   gone ahead very quickly
3. C.
   been very common
4. D.
   been impossible

Answer 1

A