Which of the following is a characteristic of reactive hazardous waste?

A characteristic of reactive hazardous waste is its ability to combust spontaneously. This means that certain materials classified as reactive hazardous waste can ignite without the need for an external heat source, under specific conditions. This property is dangerous as it can lead to uncontrolled fires and explosions, posing significant risks to both human health and the environment.

Combustibility is a key indicator of reactivity in hazardous materials, distinguishing them from non-reactive substances that do not pose similar risks. Upon encountering air, moisture, or other reactive agents, these substances can undergo rapid reactions that can lead to hazardous situations.

In contrast, the other options present attributes that do not align with the definition of reactive hazardous waste. For instance, while emitting toxic gases is a concerning quality, it does not specifically characterize reactivity. Additionally, being non-reactive with water indicates stability rather than reactivity, and stability under all conditions contradicts the definition of reactive materials, which are defined by their tendency to chemically react under certain circumstances.