Let A be the set of non-zero integers, and let R be the relation on A x A defined by (a,b) R (c,d) ↔ ad = bc. Show R is an equivalence relation.

a. Reflexive, Symmetric, Transitive
b. Symmetric, Transitive, Irreflexive
c. Reflexive, Transitive, Antisymmetric
d. Symmetric, Transitive, Reflexive