Answer:
The question did not contain any listed options. However, starch is a common white powder that will give a color change on reacting with iodine molecules
Explanation:
Iodine is a common indicator used in the lab to detect the presence of starch or starchy substances.
Iodine molecules react with amylose in starch to form a complex with a deep blue-black coloration.
Hence, a common white powder which reacts with iodine molecules to give a blue-black color must be a substance that contains starch.
