Prompted Challenge - First lines

It is said that we have two instinctual responses, fight or flight, and that we cannot know which our instincts will guide us to until we find ourselves having to choose.  I for one think it’s much simpler.  It is not a matter of instinct or of courage or bravery that makes us fight rather than take flight, it is simply a lack of options. When fight or flight becomes fight or die. In the end we will all fight.

This prompt is from Sonia Medeiros at http://doingthewritething.wordpress.com/ and is as follows;

Your challenge, should you choose to accept it, is to write either the opening or closing lines of a story. Start us off with a bang or leave us begging for more. As usual, any genre will do and the word count limit is 100.