The main idea of the passage is Baseball players and coaches use secret signals to communicate strategy to each other. How does the detail in bold develop the main idea?
If you watch a professional baseball game attentively, you will see a subtle game within
the game: a sequence of wordless signals passing among members of a team. These
seemingly arbitrary gestures-a player scratching his nose and then tapping his right
forearm, a coach tugging his cap three times in succession-are actually a secret, closely
guarded code to communicate strategy within the team. An adjustment of a cap might
be an instruction for a batter to bunt the ball; a hand in the back pocket could
indicate that a player should steal a base. As you might expect, opposing teams
expend enormous effort to crack each other's codes. For this reason, teams not only
change their codes often but also intersperse meaningless decoy signals with the real
ones, just to confuse the opposing team.
1. It illustrates the problem with verbal communication.
2. It discusses the effectiveness of certain signals.
3. It cites examples of potential signals.

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