1. In molecular orbital theory, when two atomic orbitals with wave functions $\psi_A$ and $\psi_B$ combine, they form:

   • Bonding molecular orbital by constructive interference: $\psi_{\sigma}=\psi_A+\psi_B$

   • Antibonding molecular orbital by destructive interference: $\psi_{\sigma^*}=\psi_A-\psi_B$

2. The symbol $\sigma^*$ denotes the antibonding sigma molecular orbital.

3. Therefore, its wave function is: $\sigma^* \propto \psi_A-\psi_B$

4. Now check the options:

   • A: $\psi_A+2\psi_B$ — incorrect
   • B: $\psi_A-\psi_B$ — correct
   • C: $\psi_A-2\psi_B$ — incorrect
   • D: $\psi_A+\psi_B$ — bonding, not antibonding

Hence, the correct answer is B.