Comparing acidity between groups I tried to do this using the stability of conjugate base. I can see (2) will be most stable due to resonance however my confusion lies in (1) and (3).
While in (3), the negative charge is unstable but in (1) I can't tell if it will take part in resonance because in pyridine the lone pair doesn't take part in resonance so is the same thing happening here?
The answer should be A.

Since 3 is vinylic hydrogen, therefore it is least acidic.
Both 1 and 2 are allylic and are at the alpha position with respect to the carbonyl group. 
Nitrogen is quite electronegative, therefore hydrogen 1 is more acidic than hydrogen 2. Hence the result.