unstable ?

Disclaimer: All the statements written below are purely the work of my imagination and cant guarantee any relation to known facts.

Look at your own risk

Thinking (A)

stronger acids => more unstable (as more dissociation)
(horribly wrong statement I hope)

therefore A

i will also go with (A) because it has two adjacent c=o bonds......so it will be unstable.

How does that make alpha-keto acid unstable?

I don't think we can use conjugate base concept here...that is to decide acidity. On warming(not even full-on heating), beta-keto acids quickly decarboxylate by means of six-membered transition state. So I go for (b)..can't think of anything else.
Eure please confirm.

wat abt Mesomeric effect guys ???

ya ans is b....

thx priritsh,for confirming that we had to attempt using beta keto acid concept[1]

haha!!!!!!!i was damn sure i got this wrong [1][1][1]