In this case, for the theories describing acids, we say that a Brønsted-Lowry Acid is such substance which is able to donate a H⁺ and a Brønsted-Lowry base is such substance which is able to accept a donated H⁺.
In such a way, since hydronium (H₃O⁺) is a product, meaning that water received one H⁺, we conclude water is acting as a Brønsted-Lowry base. Moreover, ammonium ion acts as Brønsted-Lowry Acid.
The correct answer is option 3. Hydrochloric acid is the most soluble in water at standard temperature and pressure because it is has a polar covalent bond which makes it a polar molecule. Water is also a polar substance therefore hydrochloric acid will really be soluble in water.
