已知向量 $\stackrel{\rightharpoonup }{a},\stackrel{\rightharpoonup }{b}$满足 $\stackrel{\rightharpoonup }{a}·\stackrel{\rightharpoonup }{b}=0,\left|\stackrel{\rightharpoonup }{a}\right|=1,\left|\stackrel{\rightharpoonup }{b}\right|=2$，则 $\left|2\stackrel{\rightharpoonup }{a}-\stackrel{\rightharpoonup }{b}\right|$=(  )

A．

$0$

B．

$2\sqrt{2}$

C．

$4$

D．

$8$