I try get it why relation divisibility is not relation partially ordered set.
$A=\{−2, 2, 4, 6, 8, 10\}$ with relation divisibility "|"
$R$ is relation divisibility | when $a,b,c \in Z : a = b \cdot c$
For relation partially ordered set must be relation:
reflexive (fulfil) - everery number could have divisible with yourself
antisymmetric (fulfil) - smaller number could have divisible with bigger, but not the otherway
transitive (not fulfil) - why please?
Divisibility is not antisymmetric on your $A$ because $-2\mid 2$ and $2\mid{-2}$.