Which of the following are chemical changes?(a) Growth of a plant(b) Rusting of Iron(c) Mixing of iron fillings and sand(d) Cooking of food(e) Digestion of food(f) Freezing of water(g) Burning of a candle.

A chemical change is a change that brings a change in the chemical properties of matter and a new substance is formed.
Examples of chemical changes from the given list of changes are:
Growth of a plant, Rusting of iron, Cooking of food, Digestion of food, and Burning of a candle.