Functional dependencies of the given subrelation R(E,D,A,B) are:
A → B
D → E
E → D
Since A is not determined by any of the given functional dependencies for R(E,D,A,B) so it must be included in the key now check whether “A” is the Primary key or not.
(A)+ = {A}
(AB)+ = {AB}
(AD)+ = {ABDE}
(AE)+ = {ABDE}
So (AD)+ and (AE)+ are the primary keys of R(E,D,A,B).
A → B, in this given FD there exist a partial dependency because here a prime key attribute(attribute which is a part of primary key but not a primary key itself of a function) which is determining a non-key attribute.
So the relation R(E,D,A,B) is not in 2NF .