Let A = {1, 2, 3} and consider the relation R = {(1, 1), (2, 2), (3, 3), (1, 2), (2, 3), (1, 3)}. Then R is 

(a) reflexive but not symmetric 

(b) reflexive but not transitive 

(c) symmetric and transitive 

(d) neither symmetric, nor transitive