Question

the main, or central, 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 others 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. it discusses the effectiveness of certain signals. it illustrates the problem with verbal communication. it cites examples of potential signals.

Explanation:

The bold - faced text gives specific examples like adjusting a cap for bunting or a hand in the back - pocket for stealing a base. These are examples of the secret signals players and coaches use to communicate strategy, which supports the main idea.

Answer:

It cites examples of potential signals.