Paramagnetism is exhibited by molecules

In which of the following ionization processes, the bond order has increased and the magnetic behaviour has changed ?

The number and type of bonds in $C_2^{2 - }$ ion in $CaC_2$ are

When $O _2$ is adsorbed on a metallic surface, electron transfer occurs from the metal to $O _2$. The $TRUE$ statement$(s)$ regarding this adsorption is(are)

$(A)$ $O _2$ is physisorbed

$(B)$ heat is released

$(C)$ occupancy of $\pi_{2 p }^*$ of $O _2$ is increased

$(D)$ bond length of $O _2$ is increased

The correct statement$(s)$ about $O _3$ is (are)

$(A)$ $O$ - $O$ bond lengths are equal.

$(B)$ Thermal decomposition of $O _3$ is endothermic.

$(C)$ $O _3$ is diamagnetic in nature.

$(D)$ $O _3$ has a bent structure.

Compare the relative stability of the following species and indicate their magnetic properties;

$O _{2}, O _{2}^{+}, O _{2}^{-}$ (superoxide), $O _{2}^{2-}$ (peroxide)