The correct option for the number of body centred unit cells in all 14 types of Bravais lattice unit cells is:
7
5
2
3
Body-centred unit cells are possible for Orthorhombic, cubic and tetragonal types of Bravais lattice unit cells.
Hence, out of the 14 possible bravais lattice, body-centred unit cells exist for only 3.
Therefore, the correct option is (4).