Enol form of acetone [CH3COCH3] exists in <0.1% quantity as monocarbonyl are more stable in keto form due to high bond energy.
CH3−
O
||
C
Keto
−CH3
Tautomerisation
──────────▶
CH3−
OH
|
C
Enol
=CH2
The enol form of acetyl acetone [CH3COCH2OCCH3] exists in approximately 15% quantity as it is stabilised by intramolecular hydrogen bonding, which is not possible in enol form of acetone.
So, both A and R are true and R is the correct explanation of A.