Firstly
the overall reaction is k2o + H2O --------> 2KOH
That above is the molecular equation
net ionic equation, as the specatator ion, the one that is not involved in the reation is in fact K+
THE NET IONIC EQUATION is therefore
O2- + H2O ------>2OH-
Acid is defined as the proton donar, in otherwards the one that donated a positve charge, here , the water donated a postive H+ ion to the O2-, SO the h2o is the acid while the O2- is the base.
Acid : h2o
Spectator ion : k+, pottasium ion