Step 1: Recall the crystal systems.
In crystallography, the seven crystal systems are: cubic, tetragonal, orthorhombic, monoclinic, triclinic, hexagonal, and rhombohedral (trigonal).
Step 2: Eliminate wrong options.
- 8: Incorrect (there are 8 Bravais lattices types in cubic only, not crystal systems).
- 6: Incorrect.
- 4: Incorrect.
Step 3: Conclusion.
Thus, there are 7 crystal systems.