Which of the following is a measure taken to prevent ESD?

Performing work on an ESD mat is a critical measure taken to prevent electrostatic discharge (ESD). ESD mats are specifically designed to dissipate static electricity safely, protecting sensitive electronic components from potential damage. These mats are usually made from materials that have conductive properties, allowing for controlled discharge of static electricity, thereby minimizing the risk of ESD events.

In contrast, using standard plastic packaging does not effectively prevent ESD; while it may offer some physical protection, it can actually contribute to static build-up. Wearing cotton clothing does not provide adequate protection against ESD either, as cotton is not a conductive material and does not help in dissipating static charges. Working on metal surfaces can introduce risks as well, because while metal itself can conduct electricity, it does not provide a safe environment for sensitive electronic components unless properly grounded. Thus, the use of ESD mats is the most effective approach among the options listed for preventing ESD.