数列 $\left\{a_{n}\right\}$ 满足 $a_{n}+a_{n+2}=2 a_{n+1}\left(n \in N^{*}\right)$, 且 $a_{1}=2, a_{2}=4$, 则 $\mathbf{a}_{9}=(\quad)$
$\because$ 数列 $\left\{\mathrm{a}_{n}\right\}$ 满足 $\mathrm{a}_{\mathrm{n}}+\mathrm{a}_{\mathrm{n}+2}=2 \mathrm{a}_{\mathrm{n}+1}\left(\mathrm{n} \in \mathrm{N}^{*}\right) \therefore$ 数列 $\left\{\mathrm{a}_{\mathrm{n}}\right\}$ 是等差数列, $\mathrm{a}_{1}=2, \mathrm{a}_{2}=4, \therefore$ 公差 $\mathrm{d}=2$, 则 $a_{9}=a_{1}+8 d=2+8 \times 2=2+16=18$. 故选 A.