Answer
B' = {a,c,d,e,f}
Work Step by Step
U = {a,b,c,d,e,f,g,h}
B = {b,g,h}
The set B' contains all the elements that are not in set B.
Since B contains b,g,h so these elements will not be there in set B.
Therefore the elements of B' are a,c,d,e,f.
B' = {a,c,d,e,f}