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: Gil Grissom:  Humans have always adapted strategies from insects . Swarming is an ancient military tactic . You surround your enemies , then attack from all directions simultaneously . Alexander the Great pioneered the maneuver 2000 years ago . Although swarms consist of several individuals , they must be treated as a single entity , which lives , thinks and moves as _ one _ , built with an internal logic to continue forward , gain momentum and never backtrack .

entity