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Resonance is defined as the way of representing the delocalization of electrons in a molecular system. It brings stability to the structures by decreasing their potential energy.

Any molecule capable of showing resonance has higher acidity as compared to those structures having no resonating structures. The hydrogen that gives rise to more extensive resonance is found to be more acidic than the hydrogen that provides less resonating forms. The hydrogen that has the highest acidity in the structure is shown below in the form of resonating structures.

Resonance in the first compound

Resonance in the second compound

The third compound exhibiting no resonance

As no resonance is possible in the case of the third compound, it is the least acidic one among the three given structures.

Hence, the order of the increasing order of acidity is shown below.