2. 职称英语
  3. Perhaps one of the best-known accidental discovery is Sir Alexander 【M1】____

Perhaps one of the best-known accidental discovery is Sir Alexander 【M1】____

游客2023-10-13  38
问题     Perhaps one of the best-known accidental discovery is Sir Alexander 【M1】______
Fleming’s discovery of penicillin. In 1922 Fleming accidentally discovered
an antibiotic that killed bacteria but not white blood cells . While suffering 【M2】______
from a cold, Fleming made a culture from some of his own nasal secretions.
As he examined the culture dish, filling with yellow bacteria, a tear fell from his 【M3】______
eye into the dish. The next day when he examined the culture, he found a clear
space which the tear had fallen. His keen observation and inquisitiveness led 【M4】______
him to the correct conclusion: the tear contained a substance that caused rapid
destruction of the bacteria, but was harmless to human tissue. The antibiotic
in the tear he named lysozyme. It turned to be of little practical importance, 【M5】______
because the germs that lysozyme killed were relatively harmless, and this discovery 【M6】______
was an essential prelude to this of penicillin, as we shall see. 【M7】______
    In 1928, Fleming was doing a research on influenza. While carrying out some 【M8】______
routine laboratory work that involved microscopic examination of cultures of
bacteria growth in petri dishes(flat glass dishes with covers), Fleming notice in 【M9】______
one dish an unusual clear area. Examination showed that the clear area surrounded
a spot where a bit of mould had fallen onto the dish, which had been left
uncovered. Remembering his experience with lysozyme, Fleming concluded that
the mould was producing something that was dead to the Staphylococcus bacteria 【M10】______
in the culture dish. Fleming isolated the mould and identified it as belonging to
the genus Penicillium, and he named the antibiotic substance it produced penicillin. [br] 【M6】
选项
答案 and—but
解析 (逗号之前指出相对来说，溶解酵素所杀死的细菌并无害，逗号后则肯定了此次发现的积极意义，前后为转折关系，因此把and改为but。)
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