A s-block element (M) reacts with oxygen to form an oxide of the...

(A) $2Mg + {O}_{2} \to 2MgO$ (Diamagnetic)
(B) $2Na + {O}_{2} \to {Na}_{2}O$ (Diamagnetic)

$2Na + \mathop{{O}_{2}}_{( \text{excess} )} \to {Na}_{2}{O}_{2}\text{(Diamagnetic)}$

(C) $2Ca + {O}_{2} \to 2CaO$ (Diamagnetic)
$Ca + {O}_{2} \to {CaO}_{2}$ (Diamagnetic)

(D) $K + \mathop{{O}_{2}}_{\text{(excess)}} \to {KO}_{2}\text{(Paramagnetic)}$