In Molecular Orbital Theory, molecular orbitals are formed by the linear combination of atomic orbitals (LCAO). The wave functions of atomic orbitals $\psi_A$ and $\psi_B$ can combine in two ways:

1. Constructive Interference: This leads to the formation of a bonding molecular orbital ($\sigma$):

$ \sigma = \psi_A + \psi_B $

1. Destructive Interference: This leads to the formation of an antibonding molecular orbital ($\sigma^*$):

$ \sigma^* = \psi_A - \psi_B $

Conclusion

The antibonding molecular orbital $\sigma^*$ is represented by:

$ \sigma^* = \psi_A - \psi_B $

Therefore, the correct answer is:

Option B: $\psi_{\mathrm{A}} - \psi_{\mathrm{B}}$