The correct option is D an equivalence relation
R = {(1, 1) (2, 2) (3, 3) (4, 4) (1, 2) (2, 1) (3, 1) (1, 3)}
As (1, 1), (2, 2), (3, 3), (4, 4) ϵ R is reflexive
(1, 2) and (2, 1) ϵ R, also (3, 1) and (1, 3) ϵ R,
∴ R is symmetric
Also.(1, 2) and (2, 1) ϵ R ⇒ (1, 1) ϵ R.
Similarly, for other elements, hence R is transitive,
∴ R is equivalence relation.