已知集合$M=\left\{-1,0,1\right\}$，$N=\left\{0,1,2\right\}$，则$M\cup N=$

$\left\{-1,0,1\right\}$ $\left\{-1,0,1,2\right\}$ $\left\{-1,0,2\right\}$ $\left\{0,1\right\}$