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. Mark Greene:  We 're going to have to do a lumbar puncture . You ever done one ?
John Carter: Uh no , but I 've seen it done .
Dr. Mark Greene: See one , do _ one _ , teach one .

puncture