This is Fishner Esterification:
You have a benzoic acid reacting with an alcohol catalyzed by sulfuric acid.
the H+ from sulfuric acid will protonate the oxygen with the double bond and you can get a resonance structure with a positive charge on the carbonyl carbon. then you know that the alcohol will attack the carbonyl carbon. the methoxy group will be deprotonated and one of the hydroxy group will be protonated and leave and now you have the ester which is D.
If you have no catalyst, this reaction would not occur as you chose.
