Cholera was a deadly disease of its day. Neither its cause nor its cure     1     (understand). So thousands of     2     (terrify) people died when there was an outbreak. John Snow wanted to solve     3     problem. He knew that cholera would not be controlled     4     its cause was found.

He became interested in two theories     5     possibly explained how cholera killed people. The first suggested that cholera     6     (multiply) in the air. The second suggested that people absorbed this disease     7     their bodies with their meals.

John Snow suspected that the second theory was correct but he needed evidence. So when another outbreak hit London in 1854, he was ready    8     (begin) his enquiry. With all the evidence he gathered, John Snow was able to announce with     9     (certain) that polluted water carried the virus.     10     (final) “King Cholera” was defeated.