What are the corresponding relation for the following three examples?

a. reflexive and symmetric but not transitive,

b. reflexive and transitive but not symmetric,

c. symmetric and transitive but not reflexive.

Answer format: a, b, or c (explain your answers)

Example I.

Consider the relation that makes no two elements related.

Example II.

Consider the set of vertices in some non-complete, non-empty graph where we make two vertices related if they are adjacent or the same vertex.

Example III.

Consider the vertices in a digraph where we have aRb if there is some possibly empty path from a to b. For example, suppose we have only the set {0, 1} and the relations 0R0, 0R1, and 1R1.