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.

Lucky:  I know you 're smart , Spot , but how do you handle pressure ? Solve this simple word problem in say , thirty seconds .
Spot: Ah - ha , no problem ! Two trains are heading toward each other , _ one _ at twenty - five miles an hour and the other at forty . They 're fifty miles apart and getting closer on the same track , but with no time to throw the switch , they collide , head on . All aboard perish and it 's all my fault !
Lucky: Next .
trains

Reinette Poisson:  There is a vessel in your world where the days of my life are pressed together like the chapters of a book so that he may step from _ one _ to the other without increase of age , while I , weary traveller , must always take the slower path .
days

Dr. Francis B. Gröss:  Perhaps the greatest disaster of all is _ one _ that man has created himself.lf nature does n't destroy the environment , it is very possible that the human being will .

disaster