6.As a well-known doctor in London,John Snow was willing to help ordinary people(61)exposed (expose) to cholera(霍亂).He knew that only when (62)the cause of it was found could the (63)deadly(dead) disease be controlled.He has two theories in mind explaining how cholera killed people.(64)Onewas that cholera multiplied in the air without reason; the other was(65)that people absorbed it into their bodies (66)with their meals.After many
(67)failures(fail),he succeeded in finding that the drinking water was to blame because the river (68)had been polluted(pollute).Without delay John Snow told the people to remove the handle from the water pump (69)so that it could not be used.Soon the disease began to slow down.To prevent the disease from (70)happening(happen) again,the water companies were instructed not to expose people to polluted water any more.Finally"King Cholera"was defeated.