1. (2023七下·深圳期中) 阅读下面短文，从所给的四个选项中选出能填入相应空白处的最佳选项。

Once in London, many people got very ill. The illness they had was called cholera(霍乱).

Doctors tried to find out how to1people from getting cholera. Most believed people got ill because of polluted air, so they told people to2their windows often and keep air fresh. They also asked3to drink lots of water and take some medicine. But their4 never helped.

John Snow, a doctor and scientist, had a5idea. He believed that the polluted water6cholera. So he went to different communities, tested the water there, and counted people who got cholera. 7, he found the cleaner the water in the community was, the fewer people would get ill.

Dr. Snow showed the findings of his study to other doctors and they knew he was8. All over London, people stopped drinking9water. They got to know how important clean water is to10