Which item is prohibited on a passenger's person or cabin baggage?

All of the items listed—workmen's tools, stunning devices, and explosive substances—are prohibited on a passenger's person or in cabin baggage due to their potential to pose significant risks to safety and security in the aviation environment.

Workmen's tools can be deemed dangerous as many could be used as weapons, facilitating theft or injury onboard the aircraft. Stunning devices, such as stun guns, are similarly classified as weapons, which can incapacitate individuals and lead to threats against crew and fellow passengers. Explosive substances are unequivocally banned due to their capacity for causing catastrophic harm and destruction, making them a high-priority threat to aviation security.

Understanding the potential dangers that each of these items presents is crucial for ensuring the safety of all passengers and crew during flights, reinforcing why such items are restricted in cabin baggage.