Which of the following relations is transitive but not reflexive for the set S = {3, 4, 6}?
a)
R = {(3, 4), (4, 6), (3, 6)}
b)
R = {(1, 2), (1, 3), (1, 4)}
c)
R = {(3, 3), (4, 4), (6, 6)}
d)
R = {(3, 4), (4, 3)}