Let's talk about it The reason of enolization is that the oxygen atom in carbonyl O=C has strong electronegativity and great attraction to electrons, which makes the double bond electrons move more to the oxygen atom, forming the form of -O-C+, and then forming the structure of HO-C=C with adjacent carbon atoms. This is called enolization. Among them,

Alkane carbonyl group (R-C=O) has a greater degree of enolization than ester carbonyl group (R-O-C = O), because the lone pair of oxygen atoms in ester carbonyl group (R-O-C = O) forms a hybrid orbit (π bond), which improves the stability of ester carbonyl group and weakens the degree of enolization. So among the three options of ABD, b >: A, this is one; The second is to consider the structural stability of the molecule after the formation of enol form. After c-option molecule is enolized, the left carbonyl group, the middle enol double bond and the right aromatic ring can form a wider range of hybridization (large π bond), and this structure is more stable. The more stable a substance is, the easier it is to form, that is, the easier it is for enolization to occur and the higher its degree is. Therefore, C is the most easily enolized substance.

Above, I hope it helps!