$$ \begin{array}{|c|c|} \hline \text{Compound} & \text{Molar Mass} \\ & \text{(grams)} \\ \hline \hline \ce{Na2O} & 62.0 \\ \hline \ce{MgO} & 40.3 \\ \hline \ce{K2O} & 94.2 \\ \hline \ce{CaO} & 56.1 \\ \hline \end{array} $$

According to the information in the table above, a 1.00 g sample of which of the following contains the greatest mass of oxygen?