Answer : The correct options is, [tex]H_2O\text{ and }H_3O^+[/tex]
Explanation :
According to the Bronsted Lowry conjugate acid-base pair concept, an acid is a substance which donates protons and a base is a substance which accepts protons.
From the given options, [tex]H_2O[/tex] and [tex]H_3O^+[/tex] represents a base-conjugate acid pair.
The balanced reaction will be :
[tex]H_2O+H^+\rightleftharpoons H_3O^+[/tex]
In this, [tex]H_2O[/tex] is a base which accepts a proton to form conjugate acid [tex]H_3O^+[/tex].
Hence, the correct options is, [tex]H_2O\text{ and }H_3O^+[/tex]
