Consider the reaction below. HF + H2O -> h3o+ F-
Which is an acid-conjugate base pair?

and

Explanation:

According to the Bronsted-Lowry conjugate acid-base theory, an acid is defined as a substance which looses donates protons and thus forming conjugate base and a base is defined as a substance which accepts protons and thus forming conjugate acid.

For the given chemical equation:

Here, is loosing a proton, thus it is considered as an acid and after losing a proton, it forms which is a conjugate base.

And, is gaining a proton, thus it is considered as a base and after gaining a proton, it forms which is a conjugate acid.

Hence, the correct answer is D.