Body-centered unit cells can be found in the following crystal systems among those listed:

1. Cubic: Body-centered cubic (BCC) is one of the lattice structures that cubic systems can have.


2. Tetragonal: A body-centered tetragonal system is also a possibility.


3. Orthorhombic: The orthorhombic system can have a body-centered orthorhombic lattice.

Therefore, the number of crystal systems from the list where a body-centered unit cell can be found is 3.