Explanation

(c)
$R = \left\{ (1,\ 3),\ (4,\ 2),\ (2,\ 4),\ (2,\ 3),\ (3,\ 1) \right\}$ is a relation on
$A = \left\{ 1,\ 2,\ 3,\ 4 \right\},$ then
(a) since, $(2,\ 4) \in R$ and $(2,\ 3) \in R$, so $R$ is not a function.
(b) since, $(1,3) \in R$ and $(3,\ 1) \in R$ but $(1,\ 1) \notin R$.
So, $R$ is not transitive.
(c) since, $(2,\ 3) \in R$ but $(3,\ 2) \notin R$, so $R$ is not symmetric.
(d) since, $(4,\ 4) \notin R$, so $R$ is not reflexive.