The correct answer is Blue-black.Concept:Plants follow the autotrophic mode of nutrition.It prepares its own food using the process of photosynthesis. The carbohydrate (starch) is prepared by the leaves of the plant in the plant in presence of sunlight and chlorophyll. The presence of the starch in the leaves can be determined by the iodine test.Explanation:Iodine TestA leaf is taken in a test tube and some spirit is poured.The leaf is completely immersed in the solution.The test tube is put in a beaker half-filled with water.The beaker is heated till all the green colour from the leaf comes out into the spirit in the test tube.The leaf was carefully taken out and washed.Place it on a watch glass and pour some iodine solution over it.The leaf will turn blue-black indicating the presence of starch.Additional InformationTranspirationWater comes out of leaves in the form of vapour by a process called transpiration.Plants release a lot of water into the air through this process.