单选题：A relation $$R$$ is defined on a set $$S$$. If for any elements

A relation $$R$$ is defined on a set $$S$$. If for any elements $$a$$, $$b$$ and $$c$$ in $$S$$, we have that if "$$a$$ $$R$$ $$b$$" is true and "$$b$$ $$R$$ $$c$$" is true, then "$$a$$ $$R$$ $$c$$" must be true, then $$R$$ is said to be __ over $$S$$. @[D](1)

A. invertive
B. symmetric
C. reflexive
D. transitive




A.invertive
B.symmetric
C.reflexive
D.transitive


答案：D