The correct option is B PbS+4H2O2→PbSO4+4H2O
Writing oxidation numbers of all the atoms,
+2 −2PbS++1−1H2O2→+2 +6 −2PbSO4++1−2H2O
The oxidation number of S has increased and O has decreased.
−2PbS→+6PbSO4 ...(i)
−1H2O2→ −2H2O ...(ii)
Increase in oxidation number of S = 8 units per PbS molecule
Decrease in oxidation number of O=1 unit per 12H2O2 molecule
=2 units per H2O2 molecule
Multiplying eq. (ii) by 4 as to make increase and decrease equal.
PbS+4H2O2→PbSO4+4H2O