If $$A = \left\{1, 2, 3 \right\}$$ and R is the relation given by
   $$R = \left\{ (1, 1), (2, 2), (3, 3), (1, 2), (2, 1) \right\}$$, then

A

R is only reflexive

B

R is an equivalence relation

C

R is only symmetric

D

R is not transitive