Answer:-
c. OH– (aq) + HCNaq) → H2O(aq) + CN– (aq)
Explanation:-
A strong base is one which is fully dissociated in aqueous solution. So if we are looking for a strong base we should be looking for OH- (aq).
Similarly a strong acid is one which is fully dissociated in aqueous solution. So if we are looking for a strong acid we should be looking for H+ (aq).
The questions is asking for a weak acid and a strong base. So our answer should have a OH- but not a H+ on the left side of the correct answer.
So our only possible answer is option C.