Which one of these is NOT listed as an ESDS component?

The correct identification of heat sinks as not being an ESDS (Electrostatic Discharge Sensitive Device) component is based on their function and construction. Heat sinks are primarily used to dissipate heat generated by electronic components to maintain optimal operating temperatures, but they do not inherently possess sensitivity to electrostatic discharge.

In contrast, RAMs (Random Access Memories), PROMs (Programmable Read-Only Memories), and CMOSs (Complementary Metal-Oxide-Semiconductors) are all types of semiconductor devices that can be easily damaged when exposed to electrostatic discharges. These components rely on intricate pathways and materials that are vulnerable to static electricity, leading to potential failures if proper handling and protective measures are not observed.

Thus, heat sinks serve a purely thermal management role and are not classified as ESDS components, clarifying why this option is the correct choice in this context.