Correct Answer - C
After the developing the sensitive emulsion of silver bromide is still present on the plate in the parts unaffected by light. Therefore it is necessary to remove it in order to get the permanent image. This process is called fixing of image. The negative plate after washing is dipped in a fixing solution of sodium thiosulphate (hypo). If dissolves unaffected silver bromide but leaves metallic silver unaffected.
`2Na_(2)S_(2)O_(3) + AgBr rarr Na_(3)[Ag(S_(2)O_(3))_(2)]+NaBr`.
