Which of the following reactions are redox reactions? Check all that apply. Which of the following reactions are redox reactions?Check all that apply. a. 4K(s)+O2(g)→2K2O(s) b. Al(s)+3Ag+(aq)→Al3+(aq)+3Ag(s) c. Mg(s)+Br2(l)→MgBr2(s) d. SO3(g)+H2O(l)→H2SO4(aq)