Which of the following equations is balanced in an acidic solution?
a. so42- + 2h2o(l) + 2e- so2(g) + 4oh-
b. so42- + 4h+ so2(g) + 4oh- + 2h2o(l)
c. so42- + 2e- so2(g)
d. so42- + 4h+ + 2e- so2(g) + 2h2o(l)

The answer
the only equation which is balanced  in an acidic solution is
D. SO42- + 4H+ + 2e-  SO2(g) + 2H2O(l)
proof:
it is an acid solution because we can see H+, presence of acid in solution
A. SO42- + 2H2O(l) + 2e- SO2(g) + 4OH- 
B. SO42- + 4H+ SO2(g) + 4OH- + 2H2O(l) are basic solution, cause we can observe on these solutions the presence of OH-, 
as for SO42- + 2e- SO2(g)    it is not an acid solution

Idon't know hope someone you

Hbr dissociates to form h+ and br-ca(oh)2 dissociates to form ca2+ and 2oh-the h+ and oh- react to form waterassuming the reactants are dissolved in water, the net reaction is h+ + oh- —> h2oif you’re asked to show all components of the reaction, the complete reaction is 2hbr + ca(oh)2 —> cabr2 + 2h2o