Answer:
(c)-He separates the larger pebbles and other debris from the finer sand by sifting it with wire mesh.
Step-by-step explanation:
A mixture is an association of substances that not react between them. It can be homogeneous when it's not possible to see the substances, or heterogeneous when it's possible to see each the substances.
Randy separates the substances of the soil with a wire mesh, so it's possible to define the substances, then the mixture is heterogeneous.