If $a_{1}, a_{2}, \ldots . .$ are in $A P$ and $\Delta=\left|\begin{array}{ccc}a_{n} & a_{n+2} & a_{n+4} \\ a_{n+6} & a_{n+8} & a_{n+10} \\ a_{n+12} & a_{n+14} & a_{n+16}\end{array}\right|$ is
(a) $a_{n}+a_{n+8}+a_{n+16}$
(b) $a_{n} a_{n+8} a_{n+16}$
(c) 0
(d) 1