please solve ques 4.22 and GIVE PROPER EXPLANATION,WORKING....

D2O contains partial charges on the atoms because of the difference in the electronegativity of D and O. Oxygen being more electronegative than Deuterium has partial negative charge and D has partial positive charge.

In the enol form the carbon atom directly attached to Oxygen also has partial positive charge (difference in electronegativity O being more electronegative than C). So, the already partially positive charged Deuterium can't attack a site which also has electron deficiency. So, it attacks the carbon next to it which is slightly electron rich when Oxygen lone pairs attack the adjacent carbon.