4. How many triad axes does a cubic crystal have? (a) 4 (b) 3 (c) 6 (d) 2 5. From the crystal systems listed below which one has the highest symmetry? (a) Orthorhombic (b) Tetragonal (c) Triclinic (d) Monoclinic 6. How many equivalent lattice directions are there in the family for a tetragonal crystal? (a) 4 (b) 8 (c) 12 (d) 6 7. What are the 2D Miller indices of the crystal vector, r, in the diagram shown below? (a) [12] (b) [22] (c) [21] (d) [21] b a