What happens when k2o dissolves in water?

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

Most likely a is the answer - because  you generate   38 atp's but also consume an atp.   each atp gives approx. less than 4 kcal so probably a is the closest answer.