Definition: In this task, you will use your knowledge about language (and common sense) to determine what element the marked number refers to. The numbers are marked with two underlines around them, like: _ number _. Your answer should be chosen from the given text, and should not contain other words.
Input: Dr. Burton:  What you need , my dear fellow , is another case . Preferably _ one _ that puts your life in danger .
Hercule Poirot: That is your advice most considered , is it ?
Dr. Burton: It 's cost you ten guineas , so I suggest you act on it .

case