e>a>d>c>b
e is the most acidic proton and b is the least.
to check for acidity, you actually have to check their conjugate base, and compare them. (remember: the stronger the acid, the weaker, or more stable, it's conjugate base will be.)
you remove the proton (H) to get the conjugate base, and compare the bases to each other.
first, you check for "charge". in this case all the conjugate bases that you form are going to have a negative charge, because you removed the hydrogen.
second, you look at the atom that carries the charge. The more electronegative and/ or larger atom will be able to hold the negative charge better, therefore more stable. and more stable means weaker base. (so weaker conjugate base = stronger acid). using this step, you will eliminate choices b,c, & d because they will have the negative charge on Carbon vs. Oxygen for a & e.
step 3: now if you have go further, you check for resonance. in this case, the negative oxygen for carboxylic acid group can be stabilized by the other oxygen, and for the alcohol group (choice a), the resonance will be using the Carbons on the benzene ring, but since having the negative charge on an Oxygen is better (more stable) than Carbon, the conjugate base of the carboxylic acid group (choice "e") will be more stable, therefore the Hydrogen "e" is more acidic than "a".
therefore "e" is the strongest acid. then "a". and after that using the resonance roue, you can arrange the rest the same way.
just in case if you had to go more further,
step 4: you look at dipole induction, ( too see if any electronegative atom close to the atom with negative charge can stabilize it)
and step 5: you look at the orbitals. ex. an sp carbon with negative charge (Carbanion) is more stable than a an sp2 Carbanion.
I hope that helped.