Which of the following compounds possess more than one percent enol content? Which of the following compounds possess more than one percent enol content?


I understood that stability of enols are dependent on the hydrogen bonding in the compounds. But here, what is the significance of more than one percent enol content?
All the compounds that have a relation $\alpha-\beta$ between the carbonyl groups. The hydrogen between two $\ce{CO}$ is very acid because two electrowithdrawing remove electron density from the $\ce{C-O}$ bond. Therefore for this kind of compound the most stable for is the enol. In Organic Chemistry this is very useful in creating new carbon-carbon bonds in mild conditions like in aldoholic reactions, Michael reactions and so on. See the very good book of Marc Loudon, Organic Chemistry.