In 1928, a Scottish scientist named Alexander Fleming returned from a holiday to find something unusual in his laboratory. He had been studying bacteria called Staphylococcus（葡萄球菌）. Before leaving, he had left some bacteria growing on culture plates. When he came back, he noticed that one plate had been contaminated（被污染）by a blue-green mould（霉菌）. What surprised him was that the bacteria around the mould had been killed. The mould had created a bacteria-free circle.
Instead of throwing the dirty plate away, Fleming became curious. He grew the mould in pure culture and found that it produced a substance（物质）that could kill many types of harmful bacteria. He named this substance “penicillin（盘尼西林）”.
However, Fleming had difficulty purifying（提纯）penicillin, and he could not produce enough of it to test on animals. For more than ten years, penicillin remained a laboratory wonder. Then, during World War II, two other scientists, Howard Florey and Ernst Chain, successfully purified penicillin. They showed that it could save the lives of wounded soldiers with infections（感染）.
Today, penicillin is known as the first antibiotic（抗生素）. It has saved millions of lives. Fleming, Florey and Chain shared the Nobel Prize in 1945. Fleming often said, “One sometimes finds what one is not looking for.”
（）1. What did Fleming notice when he returned to his laboratory?
A. All the bacteria had died.
B. The mould had killed bacteria around it.
C. The culture plates were all clean.
D. The mould had changed colour.
（）2. Why did Fleming not use penicillin on animals at first?
A. He thought it was not useful.
B. He was too busy with other work.
C. He could not purify or produce enough of it.
D. He wanted to keep it a secret.
（）3. Who finally made penicillin widely usable?
A. Alexander Fleming alone.
B. Howard Florey and Ernst Chain.
C. Fleming and his assistant.
D. Scientists during World War I.
（）4. What is the best title for this passage?
A. How to Grow Mould in a Lab
B. The History of Bacteria
C. A Lucky Accident That Saved Lives
D. The Life of Alexander Fleming

1.B 2.C 3.B 4.C

1. 细节理解题：根据原文第一段“What surprised him was that the bacteria around the mould had been killed.”可知，弗莱明回到实验室后注意到霉菌杀死了它周围的细菌。A选项“所有细菌都死亡”表述错误，仅霉菌周边的细菌被杀死；C选项“所有培养皿都干净”、D选项“霉菌改变了颜色”原文均未提及，因此选B。
2. 细节理解题：根据原文第三段“However, Fleming had difficulty purifying(提纯) penicillin, and he could not produce enough of it to test on animals.”可知，最初弗莱明无法在动物身上测试青霉素的原因是他没法提纯青霉素，也生产不出足够的量。A、B、D选项的内容原文均没有相关表述，因此选C。
3. 细节理解题：根据原文第三段“Then, during World War II, two other scientists, Howard Florey and Ernst Chain, successfully purified penicillin. They showed that it could save the lives of wounded soldiers with infections.”可知，最终让青霉素可以广泛投入使用的是Howard Florey和Ernst Chain两位科学家，因此选B。
4. 主旨大意题：全文讲述了弗莱明在度假返回实验室时意外发现霉菌可以杀死细菌，进而发现青霉素，后续经其他科学家完善后拯救了数百万生命的故事，对应C选项“一个拯救生命的幸运意外”作为标题最贴切。A选项“如何在实验室培育霉菌”、B选项“细菌的历史”、D选项“亚历山大·弗莱明的一生”都不能概括全文核心内容，因此选C。