Please help!! Chemistry!! Important!! Will mark brainiliest

1. The half-reaction 2MnO2 + H2O + 2e- Mn2O3 is missing
a. electrons
b. OH- ions
c. Mn2+ ions
d. O2- ions

2. The oxidation number of S in SO2−4 is
a. 2
b. +2
c. +4
d. +6