Which of the following equations represents a redox reaction?

A. HNO3(aq) +NaOH(aq) →NaNO3(aq)+H2O(l)
B. AgNO3(aq) +KCl(aq) →AgCl(s)+KNO3(aq)
C. CaCO3(s) →CaO(s)+CO2(g)
D. 2H2S(s)+SO2(g) →2H2O+3S(g)

Correct Answer: Option D

D. 2H2S(s)+SO2(g) →2H2O+3S(g)