The binary relation $R$ on $X = \{a, b, c, d\} $ is given by $R = \{(a, a), (a, b), (b, b), (c, c), (c, d), (d, c)\}$.
Determine if $R$ is reflexive, symmetric, anti-symmetric and / or transitive.
My solution is that I thought it was symmetric because of $cRd \Longrightarrow dRc.$
It is wrong. In the answer they say it is none of reflexive,symmetric, anti-symmetric, and / or-transitive??