Which one of the following CANNOT be used as self-lubricating bushings?

Plastic bushings cannot be used as self-lubricating bushings because they typically lack the necessary self-lubricating properties found in other materials. Self-lubricating bushings are designed to reduce friction while providing durability in various applications, and these often involve composite materials, metals, or specially formulated plastics that include additives to enhance lubrication.

In contrast, sleeved bushings, metal bushings, and reinforced fiber bushings often have characteristics that allow them to function effectively with or without additional lubricants. For instance, metal bushings may incorporate lubricating properties through the use of specific alloys or coatings, while reinforced fiber bushings typically come with embedded lubricants that create lower friction surfaces. This understanding highlights how the choice of material is crucial in applications where lubrication is critical for performance and longevity.