Answer:
B. Decomposition reaction
Step-by-step explanation:
When silver chloride is kept in the sun, it decomposes to form chlorine gas and silver. As the reaction proceeds, the white coloured silver chloride turns grey because of the formation of silver. Chlorine produced in the reaction escapes into the environment as it is produced in the gaseous state.
2AgCl(s) + light → 2Ag(s) + Cl²(g)
As the above reaction is sensitive to light, they are used in black and white photograph.