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. Tom Loman:  I 'm afraid I have bad news . Liver temp 's eighteen degrees below normal .
Lieutenant Horatio Caine: She died within the last twelve hours .
Natalia Boa Vista: We 've been following Esteban for _ twenty _ - four .
Detective Frank Tripp: So he could n't have done this .
Lieutenant Horatio Caine: We just became his alibi .

hours