1．he________(对……感兴趣)two theories explaining how cholera killed people. 2．the cholera outbreak was so severe that________ (超过)500 people had died in 10 days. 3．john________(调查)the source of the water for these two streets. 4．to________ this________(阻止)happening again，john snow suggested that the source of all water supplies be examined.
