Cholera was a   (dead) disease of its day. Neither its cause nor its cure    ( be) understood. So many thousands of   ( terrify) people died    there was an outbreak. John Snow wanted to solve the problem. He knew that cholera would never be controlled its cause was found.
He became interested in two theories   possibly explained how cholera killed people. The first suggested that cholera   ( multiply) in the air. The second suggested that people absorbed this disease  their bodies with their meals.
John Snow suspected that the second theory was correct but he needed evidence. So when another cholera    London in 1854, he was ready to begin his enquiry. With all the evidences he gathered ,John Snow was able to announce with  (certain) that polluted water carried the virus. Finally “King Cholera” was defeated.