完形填空II. 根据所学语段，用适当的词填空。请同学们务必看清题目要求，限做指定题目。(共8个小题；每小题1分，满分8分)
(长郡生试题)   Another drug that has helped increase the standard of people’s   41  is penicillin. This bacteria-killing medicine is considered by many to be one of the most   42   medicines in contemporary society. It was discovered by   43  Scottish scientist named Alexander Fleming in 1928. He noted that mould had grown on a special transparent jelly that had bacteria on it. Fleming tried this mould   44  on another bacterium and found that it killed the bacteriun   45  . He named the chemical found in the mould ‘penicillin’ and tried to make it pure to be a medicine.
46    , it was not until World War Ⅱ   47  two other scientists managed to use new chemical techniques to purify it. They were able to produce it in large    48   .