Final answer:
Option (D) A mixture of a solid in another solid is an example of a heterogeneous mixture. This is because in a heterogeneous mixture, the components are not evenly distributed and can be individually distinguished.
Step-by-step explanation:
In the choices given, the heterogeneous mixture would be (D) A mixture of a solid in another solid. A heterogeneous mixture is a mixture where the constituents are unevenly distributed or where you can see the different components of the mixture. An example of a mixture of a solid in another solid that is heterogeneous could be something like a bowl of mixed nuts. Each component (each type of nut) remains distinct and can be visually distinguished from the others.
Learn more about heterogeneous mixture