Answer: the strongest base will be A) HX(aq)
Explanation:
The cationic part of the base is formed from the cation in the weak acidic salt solution, (say Na2CO3= HY, and H= Na) i.e H+, whereas the anionic part of the base comes from the the weak base ( say NH4OH= HX, and X= OH-)
Then the strong base formed will be HX