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

A relation $$R$$ is defined on a set $$S$$. If for every element $$e$$ in $$S$$, "$$e$$ $$R$$ $$e$$" is always true, then $$R$$ is said to be __ over $$S$$. @[D](1)

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




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


答案：D