Identify the base in this acid-base reaction:

2 upper H upper C subscript 2 upper H subscript 3 upper O subscript 2 plus upper M g (upper O upper H) subscript 2 right arrow upper M g (upper C subscript 2 upper H subscript 3 upper O subscript 2) subscript 2 plus 2 upper H subscript 2 upper O.
HC2H3O2

Mg(OH)2

Mg(C2H3O2)2

H2O