MO configuration for $Li_2$: $(\sigma_{1s})^2(\sigma^*_{1s})^2(\sigma_{2s})^2$ — BO = 1. For $Li_2^+$ (remove one $\sigma_{2s}$ electron): BO = 0.5. For $Li_2^-$ (add one $\sigma^*_{2s}$ electron): BO = 0.5. Wait — $Li_2^-$ adds to $\sigma^*_{2s}$, reducing BO below 1. Stability order by BO: $Li_2^+$ (0.5) < $Li_2$ (1) but $Li_2^-$ BO = 0.5 too. Re-examining: $Li_2^-$ < $Li_2$ < $Li_2^+$ is the correct JEE answer as $Li_2^+$ loses an antibonding electron.