Answer
2S (aq) + 2HNO_{3} (aq) + H_{2}O (l) → 2H_{2}SO_{3} (aq) + N_{2}O (g)$
Oxidizing Agent: $HNO_{3}$
Reducing Agent: S
Work Step by Step
We add water to left side to balance the equation as it is in acidic medium. Oxidation state of S is changed from 0 to +4, hence it is oxidized and state of N is changed from +5 to +1, hence it is reduced.