Cholera used to be one of the most feared diseases in the world, until a British doctor, John Snow, showed how it could be o    1    . This illness causes s    2    diarrhea, dehydration, and even death. In the early 19th century, when an outbreak of cholera hit Europe, millions of people died from the disease. As a young doctor, John Snow became f    3    , because no one knew how to prevent or treat cholera. In time, he rose to become a famous doctor, and even a    4    to Queen Victoria when she gave birth. However, he never lost this d    5    to destroy cholera once and for all.

In general, doctors in those days had two c    6    theories to explain how cholera spread. One theory was that bad air caused the disease. Another was that cholera was caused by an i     7     from germs in food or water. Snow s     8     to the second theory. It was correct, but he still needed p    9    . Consequently, when an outbreak of cholera hit London in 1854, Snow began to investigate. He discovered that in two particular streets the cholera outbreak was so severe that more than 500 people died in ten days. He was d    10     to find out why.

John Snow was a famous doctor in London—so expert, indeed,     1     he attended Queen Victoria as her personal physician. But he became inspired when he thought about helping ordinary people     2     to cholera. This was the deadly disease of its day. Neither its cause     3     its cure was understood.

Through Snow’s tireless efforts, water companies began to sell clean water and the threat of cholera around the world saw a     1         2    . However, cholera is still a problem. Each year, millions of people around the world get cholera and many die     3     it. Fortunately, we now know how to prevent cholera, thanks to the work of John Snow. Moreover, in his use of maps and     4    . Snow     5     the way scientists study diseases. For this reason, Snow is considered the father of modern epidemiology.

Yuan Longping, known as the “father of hybrid rice”, considers himself a farmer. His slim but strong body is just like that of millions of Chinese farmers, to whom he has d    1     his life.

Yuan was born in 1930 in Beijing. His parents wanted him to pursue a career in science or medicine. However, what concerned him most was that farmers often had poor harvests and sometimes had a serious s    2     of food. To t    3     this crisis, he chose to study agriculture in a college.

After graduating in 1953, he worked as a researcher. Yuan realised that larger fields were not the solution. Instead, farmers needed to b    4     yields in their fields. How this could be done was a challenging question. Yuan was c    5     that the answer could be found in the creation of hybrid rice. One characteristic of hybrids is that they usually a    6     a higher yield than c    7     crops. Through i     8     effort, Yuan o    9     technical difficulties to develop the first hybrid rice. This hybrid enabled farmers to expand their o    10     greatly.

Tu Youyou, a c    1     and patient scientist, was born in Ningbo, China, on 30 December 1930, and graduated from Peking University Medical School in1955. After she graduated, she worked at the China Academy of Traditional Chinese Medicine in Beijing. In 1967, the Chinese government f    2     a team of scientists with the o    3     of discovering a new treatment for malaria, and Tu Youyou was among the first researchers c    4    . In the b    5    , Tu Youyou went to Hainan, where malaria was more c    6    , to study malaria patients. In 1969, she became the head of the p    7     in Beijing, and decided to review ancient Chinese medical texts to find traditional b    8     treatments for the disease. Her team examined over 2,000 old medical texts, and evaluated 280,000 plants for their medical properties. From their research, they discovered and tested 380 d    9     ancient Chinese medical treatments that showed p    10     in the fight against malaria.