In 2,4-hexadione if H+ is removed from carbon number 3 then it will cause delocalisation of electrons from oxygen on carbon number 2 to oxygen on carbon number 4
which will stabilise the carbanoin thus formed.This stabilization is the most in case of 2,4-hexadione.
- Swarna Kamal Dhyawala why u r seeing the stability the question of which these has most no. of acidic hydrogen .. and option (c) has most no.acidic hydrogen