Concept:Boiling the leaf in water first kills the cells and stops enzyme activity.Explanation:In the starch test, the leaf is boiled in water for about a minute to kill the cells.This stops enzymatic activity and makes the cell membranes more permeable.Chlorophyll is dissolved out later when the leaf is boiled in alcohol, not in water.Boiling in water also does not harden the cell walls.Killing the cells prepares the leaf for decolourisation and for iodine to act properly.Answer:B. cells are killed