Which of the following are double-displacement reactions? multiple answers
A. 2H2(g) + O2(g) -> 2H2O(g)
B. Zn(s) + 2HCI(aq) -> H2(g) + ZnCI2(s)
C. Ba(OH)2(aq) + 2HCIO4(aq) -> Ba(CIO4)2(aq) + 2H2O(I)
D. HNO3 (aq) + KOH (aq) -> H2O(I) + KNO3 (aq)​