Answers: The most acidic is D and the most basic is A.
I'm kinda confused on this. I looked at the base NH one and saw that when it was protonated it lost its aromaticity. So as a result, the NH²⁺ one must be an unstable acid, thus it is the stronger acid. The stronger acid must have the stronger base on the same side, thus I concluded that A is stronger than B. Is this the correct way to think about it?
When I compare the two bases on each side (the O⁻ and OH⁺ one), I see that the O⁻ one is more stable (on the left side), thus it is the weaker base, meaning the OH⁺ one (on the right side) is the stronger base. However, that is not right as A is the strongest.
However, when I compare the two acids on each side. I see that the OH one (right side) is more stable, thus it must be the weaker acid, so its conjugate base which is the O⁻ one must be stronger. This way of thinking got me the correct answer. However, I'm still unsure if this is the reason why as I was always told to compare the charged species.
Also E doesn't have a lone pair to donate, so I neglected that in the conversation of the strongest base. For C, it just didn't seem likely to me.