Which of the following formulations contains a finely ground inert substance mixed with active ingredient?

The formulation that contains a finely ground inert substance mixed with the active ingredient is referred to as dusts. Dusts are typically composed of a small percentage of the active ingredient and a larger proportion of an inert carrier material that allows for easy application and distribution without clumping. This formulation is particularly effective for targeting insects or diseases as the fine particles can easily adhere to surfaces and penetrate into crevices.

In contrast, baits are designed to attract pests and contain a mixture of active ingredients along with a food substance to lure the target organism. Granules and pellets contain active ingredients with larger inert particles, making them suitable for soil application or targeted delivery to specific areas, rather than the fine particulate nature characteristic of dusts. Ultra-low volume formulations consist of concentrated active ingredients that are diluted with little solvent, intended for very low-volume applications, and do not contain finely ground inert substances in the same way that dusts do. Hence, dusts are the correct answer as they specifically meet the criteria presented in the question.