The decreasing order of basic character of $K_{2}O,BaO,CaO$ and $MgO$ is ___________.

The correct option is A $K_{2}O>BaO>CaO>MgO$
The decreasing order of basic character is $K_{2}O>BaO>CaO>MgO$

With increase in the charge of the metal cation or with decrease in the size of metal cation, the basic character of its oxide decreases. This is due to increase in charge density.

Hence, the correct option is $A$.