Concept:Testing a leaf for starch follows a fixed sequence: killing the leaf, decolourising it, softening it, and then adding iodine solution.
Explanation:First, boil the leaf in water to kill its cells and stop enzymatic activity.
Next, boil the leaf in alcohol to remove chlorophyll and decolourise it.
Then, wash the leaf in warm water to soften it and make it permeable to iodine.
Finally, add iodine solution to the leaf; the formation of a blue-black colour confirms the presence of starch.
Hence, the required sequence is I, II, III and IV.
Answer:A. I, II, III and IV