Answer:
Option C, hexagonal crystal system
Step-by-step explanation:
1. A hexagonal crystal family has two crystal systems with in it . They are
a) trigonal and
b) hexagonal
2.The smallest unit within an isometric crystal system has the shape of cube which is the most common shapes of the crystals.
3. In monoclinic crystal system, the crystal have unequal vector lengths just like an orthorhombic system
4. Triclinic crystal system consists of unequal axes that are inclined at nonperpendicular angles relative to each other.
Hence, option C is correct