>**Question**

> How would you compare the acidity of the most acidic proton in each of the following molecules?

>1. ![enter image description here][1]


>2. ![enter image description here][2]


>3. ![enter image description here][3]


  [1]:https://i.sstatic.net/MsgCW.png
  [2]:https://i.sstatic.net/KNvay.png
  [3]:https://i.sstatic.net/Vwwur.png

The answer says 3 is the most acidic, followed by 1, and finally 2 is the least acidic. Can someone please tell me how to determine this? I know the benzene group is electron donating group, but am not quite sure how to correlate this knowledge with determining the relative acidities.