What must a fencer do to indicate readiness before starting a bout?

To indicate readiness before starting a bout, a fencer must adopt a fencing stance and signal readiness to the referee. This action is crucial in demonstrating that the fencer is prepared both mentally and physically to engage in the bout. The fencing stance signifies that the fencer is in the proper position to begin, ready to react to their opponent.

Adopting this stance and signaling to the referee ensures clarity in communication and confirms that both fencers are set to start interacting in a controlled manner. This process is essential for maintaining the flow of the competition and ensuring that both fencers are on the same page when the bout commences. Effective signaling to the referee also helps manage the match's pace and reflects sportsmanship in observing the formalities of the sport.

The other choices do not align with standard practices in fencing. Bowing to the audience, for example, is not customary as a readiness indicator, nor is sitting down before starting, which goes against the principle of being prepared for action. Simply wearing protective gear without confirming readiness lacks the necessary communication that is inherent to the sport's etiquette and rules.