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: Professor River Song:  You 're doing a very good job acting like you do n't know me . I 'm assuming there 's a reason .
The Doctor: Well , a fairly good _ one _ , actually .
Professor River Song: OK , shall we do diaries then ? Where are we this time ? Ah , going by your face , I 'd say it 's early days for you , yeah ? So , um - crash of the Byzantium . Have we done that yet ?
Professor River Song: Obviously
Professor River Song: ringing no bells . Right , um - oh , picnic at Asgard . Have we done Asgard yet ?
Professor River Song: Obviously
Professor River Song: not . Blimey , very early days , then . Hoo ! Life with a time traveler - never knew it could be * such * hard work . Um ...
Professor River Song: Look
Professor River Song: at you .
Professor River Song: You 're * young*.
The Doctor: I 'm really not , you know .
Professor River Song: No , but you * are*.
Professor River Song: Your eyes . You 're younger than I 've ever seen you .
The Doctor: You 've ... seen me before then ?
Professor River Song: Doctor
Professor River Song: . Please tell me you know who I am .
The Doctor: Who are you ?

reason