Comparing acidity in 3,4-dihydroxyfuran-2(5H)-one and 2,3-dihydroxycyclopent-2-en-1-one

I have two compounds with two hydrogens namely (a),(b),(c) and (d). I have to compare the acidity of the following hydrogens.


[![](https://i.stack.imgur.com/DrLp5.png)](https://i.stack.imgur.com/DrLp5.png)


My approach:


I removed the hydrogen atoms one by one and compared the stabilities, as there are most resonating structures for (a) it will be most stable (most acidic too). Then followed by (b), (c) and (d). 


But the answer is given different without any further explanation. Does anybody have the right approach to tackle these type of questions?


