下列化学反应属于右边关系图中阴影部分的是(      )

$CuO+CO\stackrel{\mathrm{加热}}{=}Cu+C{O}_2$ $2H_{2}0\stackrel{\mathrm{通电}}{=}2H_2$↑ $+O_2$↑ $CaO+H_{2}O=Ca(OH{)}_2$ $2NaOH+H_{2}S{O}_4=N{a}_{2}S{O}_4+2H_{2}O$