In this problem, always compare the conjugated base when you are comparing which is the strongest acid. Our first rule is to check the charge, and looking at all our conjugated based, you should see that all the molecules are (-) except the carboxylic acid. A negative charge is a great indicator that it is a stronger conjugated base, therefore it will be a weaker acid. This concludes that the Carboxylic acid is the weaker conjugated base, and is the strongest acid compare to the other three.
Next, we are going look at the atom because F and O both have the same charge, -1. If we are comparing F to O, we want to see if the atom is either very small or strong in electronegativity. This will indicate the stableness of the molecule, and we know the more stable the conjugated base, the weaker. The reason why it is more stable with a small atom is because the electrons are getting closer to the nucleus (protons + neutrons), so the electrons are attracted to the nucleus. The reason why it is more stable for stronger electronegativity is because the electrons can be withdrawn, and this will make it closer to neutral. The aforementioned is the reason for stability, and thus a weaker acid. Since we are comparing F and O, we know that O is more electronegative and is more stable. This will conclude that F is the stronger acid, and will be ranked second based on our rules.
I am sure you understand between alcohol and the carbonyl is because of resonance. Good job on that one!
