Question

    The cold is the most common of man’s ailments(疾病). Yet it stumped(难住)the medical authorities. Many of more terrible diseases have come under the control of modem man as the result of the knowledge gained in the lab of science research. Investigators have thought that the cold is usually caused by 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 to which the disease can be given experimentally. The use of this animal is limited by its cost and by the fact that so many of the animals die of pneumonia during the experiments. This leaves for all practical purposes only human volunteers to be used in research projects. Many people of prisons have helped in this work, but because of .these limitations, research into the cause and cure of colds has progressed very slowly.

Research into the cause and cure of colds has________.

A．gone ahead very slowly

B．gone ahead very quickly

C．been very common

D．been impossible

 

Answer 1

答案：A
提示：

从最后一句话就能看出进展缓慢。