Answer:
The correct answer is option A.
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:
[tex]NH_3+H_2O\rightleftharpoons NH_4^{+}+OH^-[/tex]
Here, [tex]H_2O[/tex] is loosing a proton, thus it is considered as an acid and after losing a proton, it forms [tex]OH^-[/tex] which is a conjugate base.
And, [tex]NH_3[/tex] is gaining a proton, thus it is considered as a base and after gaining a proton, it forms [tex]NH_4^{+}[/tex] which is a conjugate acid.
Hence, the correct answer is option A.
