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: Gen. Earle 'Buzz' Wheeler:  The bridge is a major target , and we 've never hit it . Chances of civilian deaths will be almost zero .
Robert McNamara, Secretary of Defense: I say 100 to 500 , possibly more !
Lyndon Baines Johnson: Which is it ? _ 500 _ or zero ?

Chances