In the set of animals, a relation $R$ is defined in each question.
a $\mathrm{R} \mathrm{b}$ if ${ }^{\prime \prime} \mathrm{a}$ and $\mathrm{b}$ are in different zoological parks," then $\mathrm{R}$ is
(1) only reflexive
(2) only symmetric
(3) only transitive
(4) equivalence