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: Tegan Jovanka:  Doctor , why ca n't you help them ?
The Doctor: Do n't you understand ? If I did , it would be the end of me as a Time Lord .
Tegan Jovanka: What do you mean ?
The Doctor: I can only regenerate twelve times . I have already done so four times .
Tegan Jovanka: So ?
The Doctor: Do n't you see ? Eight of them ; _ eight _ of me .
Tegan Jovanka: They want your remaining regenerations ?
The Doctor: It 's the only way to end their mutation .

regenerations