Final answer:
Graphite and diamond are polymorphs, both composed of carbon but with different internal structures, leading to their distinct physical properties.
Step-by-step explanation:
The correct answer to the question "Which of the following pairs of minerals are polymorphs of each other?" is b) Graphite and Diamond. Polymorphs are minerals that have the same chemical composition but different internal atomic arrangements and crystal structures. While both graphite and diamond are composed of carbon, the arrangement of carbon atoms in diamond forms a three-dimensional tetrahedron which gives it a hard structure. In contrast, the carbon atoms in graphite are arranged in planar layers composed of six-membered rings, which makes graphite soft and slippery.