Which of the following is an example of equipment that might use shear wire?

Shear wire is commonly used in various applications where a mechanical component needs to be released or activated at a predetermined load or stress level. In the context of fire extinguishers, shear wire is often employed in the mechanism that holds the extinguisher's latch in place until it needs to be deployed. When the handle is pulled, the shear wire breaks, allowing the extinguishing agent to be released effectively.

In contrast, while electrical circuits, landing gear mechanisms, and avionics systems can utilize various forms of safety and release mechanisms, they typically don't rely on shear wire. Electrical circuits are more associated with conductive paths and circuits openings. Landing gear systems might use hydraulic or pneumatic systems for extension and retraction. Avionics systems focus on electronic components and data communication rather than mechanical release methods like shear wire. Therefore, the use of shear wire is most fittingly illustrated by fire extinguishers.