Which of the following actions would likely cause a timeout during a bout?

A timeout during a bout is typically called in situations that require immediate attention or intervention, which includes injuries to a fencer. When a fencer is injured, it is essential for the referee to pause the bout to ensure the well-being of the athlete and assess the situation. This allows medical personnel to attend to the injured fencer, ensuring their safety and compliance with competition regulations.

In contrast, actions like a hold on the weapon or changing sides do not inherently require a timeout. These are situations that can be resolved without interrupting the flow of the bout. Scoring a hit is also part of the regular progression of a bout and does not necessitate a stoppage. Therefore, a timeout is most appropriately warranted when addressing an injury, highlighting the health and safety priorities in fencing competitions.