Which of the following is NOT a suitable payload for bottom dumping?

Bottom dumping involves releasing material directly underneath a vehicle using a dump mechanism. This method is efficient for materials that flow easily and can spread out when dumped.

Sand, gravel, and dirt are all suitable payloads for bottom dumping because of their granular nature, which allows them to fall freely and spread out evenly when released. These materials facilitate quick and uniform distribution, making them ideal for uses such as road construction, landscaping, or filling.

In contrast, boulders are significantly larger and heavier objects that do not flow like granular materials. When dumped, they can cause unevenness, may not spread effectively, and could potentially damage the dump mechanism or the vehicle if the weight and size exceed the designed capabilities of the dumping system. Therefore, utilizing boulders in a bottom dump scenario is not practical or safe.