What was a common risk for bored workers in factories?

Bored workers in factories often faced a heightened risk of injury. This is primarily because a lack of engagement and focus can lead to decreased awareness of one's surroundings and the machinery being used. When workers become disengaged or inattentive, they may fail to follow safety protocols, miss warning signs, or make mistakes while operating equipment, all of which can lead to accidents and injuries.

In contrast, the other options either represent positive outcomes or opportunities that do not typically correlate with boredom in a factory setting. For instance, promotion and training opportunities are generally linked to performance, skill development, and job involvement, not disengagement. Similarly, job satisfaction is generally low in research indicating that boredom often correlates with dissatisfaction rather than fulfillment in the workplace. Hence, the significant risk factor for bored workers is indeed injury due to their diminished concentration and vigilance.