The answer should be D all of the above
H3O+(aq) + OH-(aq) --> 2H2O (l)
NaHCO3(s) --> NaH 2+ (aq) + CO3 2- (aq)
NaH 2+ (aq) + H2O (l) --> Na+ (aq) + H3O+ (aq)
H2O (l) + CO3 2- (aq) --> OH- (aq) + HCO3- (aq)
(I'm not completely sure if I did the third question right) I'm sorry if I got it wrong
6 miles of H2O is equal to 12 Hydrogen molecules and 6 oxygen molecules. Equaling 18 in total.