Enols are basically alkenes so any factor that stabilise alkene also stabilise enol Hence D will answer. Further H bonding is responsible for any enol formation in option C and D. Thanks
The two main factors affecting the stability of the enol forms are
- Hydrogen Bonding
What @Ankith_2020 said is right. Formation of double bond is stable and Hydrogen bonding will result in more stability. Hence more chance of formation of enol.