设集合 $M=\left\{x\right|x^2+2x=0,x\in R\}$, $N=\left\{x\right|x^2-2x=0,x\in R\}$,则 $M\cup N=$(  )

A．

$\left\{0\right\}$

B．

$\{0,2\}$

C．

$\{-2,0\}$

D．

$\{-2,0,2\}$