What makes a pure substance different from a heterogeneous mixture?

a) The components of a pure substance are mixed unevenly instead of evenly within the pure substance.

b) Insoluble instead of soluble particles are suspended within the pure substance.

c) Two liquids that normally are not mixable are mixed in a heterogeneous mixture.

d) The components of a pure substance are single elements or compounds instead of a mixture of compounds.

d) The components of a pure substance are single elements or compounds instead of a mixture of compounds.