Which of the following crystal system has four types of unit cells?

The seven crystal systems and the number of Bravais lattices they possess are as follows:

Cubic: $3$ (Primitive, Body-centered, Face-centered)
Tetragonal: $2$ (Primitive, Body-centered)
Orthorhombic: $4$ (Primitive, Body-centered, Face-centered, End-centered)
Hexagonal: $1$ (Primitive)
Rhombohedral: $1$ (Primitive)
Monoclinic: $2$ (Primitive, End-centered)
Triclinic: $1$ (Primitive)

The orthorhombic crystal system is the only one that has all four types of unit cells.

Answer: Orthorhombic