Bond order normally gives idea of stability of a molecular species. All the molecules viz.  ${\mathrm{H}}_2,{\mathrm{Li}}_2\text{ and }{\mathrm{B}}_2$have the same bond order yet they are not equally stable. Their stability order is 

None of the given option is correct. The molecular orbital configuration of the given  molecules is 
$$\begin{gathered} {\mathrm{H}}_2=\mathrm{\sigma }1{\mathrm{s}}^2\text{ (no electron anti-bonding) } \\ {\mathrm{Li}}_2=\mathrm{\sigma }1{\mathrm{s}}^2{\mathrm{\sigma }}^{\ast }1{\mathrm{s}}^2\mathrm{\sigma }2{\mathrm{s}}^2\text{ (two anti-bonding electrons) } \\ {\mathrm{B}}_2=\mathrm{\sigma }1{\mathrm{s}}^2{\mathrm{\sigma }}^{\ast }1{\mathrm{s}}^2\mathrm{\sigma }2{\mathrm{s}}^2{\mathrm{\sigma }}^{\ast }2{\mathrm{s}}^2\left\{\mathrm{\pi }2{\mathrm{p}}_{\mathrm{y}}^1=\mathrm{\pi }2{\mathrm{p}}_{\mathrm{z}}^1\right\} \\ \text{ (4 anti-bonding electrons) } \end{gathered}$$
Though the bond order of all the species are same (B.O =1) but stability is different. This is due to difference in the presence of no. of anti-bonding electron. Higher the no. of anti-bonding electron lower is the stability hence the correct order is $H_2>{Li}_2>B_2$