6.下列化學反應中,何者為氧化還原反應?(A) HCI(aq)+ NaOH(aq) →NaCI(aq)+H2O+H2O(l)(B) 2Na(s)+2H2O(I) →2NaOH(aq)+H2(g)(C) CaO(s)+ H2O(I)→Ca(OH)2(s)(D) 2HCIO4(aq)+CaCO3(s)→Ca(ClO4)2(aq)+H2O(l)+CO2(g)