Which maintenance stand is referred to as a nonadjustable 4-foot platform?

The maintenance stand referred to as a nonadjustable 4-foot platform is indeed the C-1 stand. This stand is specifically designed for various maintenance tasks that require a stable and elevation-providing platform without the need for adjusting its height.

This characteristic of being nonadjustable makes it suitable for situations where a consistent height is desired, aiding in safety and efficiency during maintenance operations. Other stands mentioned may have different functionalities or adjustable features that do not align with the description of being a nonadjustable 4-foot platform. Therefore, the C-1 stands out as the correct choice due to its specific purpose and design simplicity, catering to maintenance needs that demand a fixed height.