Listed are several pairs of substances. For some pairs, one or both members of the pair react individually with water to produce a gas. For others, neither member of the pair reacts with water. The pair for which each member reacts with water and yields the same gaseous product is 

(a) Al(s) and Ba(s); 

(b) Ca(s) and CaH₂(s);

(c) Na(s) and Na₂O₂(s);

(d) K(s) and KO₂(s);

(e) NaHCO₃(s) and HCl(aq).