Question

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.
what is the main, or central, idea of the passage?

Explanation:

The passage describes the use of non - verbal signals (gestures) in professional baseball games as a secret code for teams to communicate strategy. It also mentions that opposing teams try to crack these codes, so teams change codes often and use decoy signals. The central idea is about the secret, strategic non - verbal communication (through signals/codes) in professional baseball and how teams deal with opposing teams' attempts to decipher these codes.

Answer:

The main idea of the passage is that in professional baseball games, teams use subtle, secret non - verbal signals (a coded system of gestures) to communicate strategy, and they frequently change these codes and use decoy signals to prevent opposing teams from cracking them.