Answer
D' = {g}
Work Step by Step
U = {a,b,c,d,e,f,g}
D = {a,b,c,d,e,f}
Find D'
Set D' includes all the elements in 'U' that are not in set D.
Since set D contains {a,b,c,d,e,f} so these elements cant be in set D.
Therefore the elements of set D' is g.
Therefore D' = {g}