Answer
Remove a H+ ion from the oxygen of each compound to get their conjugate bases. This leaves a negative charge on the oxygens.
Work Step by Step
Move the negative charge onto other oxygens in the compound to form resonance forms. The first four bases all have resonance forms because the negative charge can move onto other oxygens (it can also be moved to other electronegative atoms but in this problem, the electronegative atoms are oxygens) whereas the last base has no resonance forms as it has only one oxygen.
