Answer
It is an arithmetic sequence.
$d=-2$
Work Step by Step
A sequence is arithmetic if $a_2-a_1=a_3-a_2=a_4-a_3=a_5-a_4=...=d$
For the given sequence we have that:
$a_2-a_1=8-10=-2$
$a_3-a_2=6-8=-2$
$a_4-a_3=4-6=-2$
$a_5-a_4=2-4=-2$
It is an arithmetic sequence.
Common difference: $d=-2$
