In preparing match sticks, the ingredient used is option 3, which is red phosphorus.

Option 1, Chile saltpetre, is not used in the preparation of match sticks. It is a naturally occurring nitrate mineral primarily used as a fertilizer.

Option 2, Indian saltpetre, also known as potassium nitrate or niter, is not used in preparing match sticks either. It is commonly used in the production of gunpowder and fireworks.

Option 4, sodium bicarbonate or baking soda, is not used in match stick preparation. It is a common ingredient in baking and cooking, often used as a leavening agent.

Red phosphorus, on the other hand, is a key ingredient in the striking surface of match sticks. When the match is struck against a rough surface, the friction causes the red phosphorus to ignite and create a flame. This reaction allows the match to light up and be used for various purposes.

Therefore, option 3, red phosphorus, is the correct answer for the ingredient used in preparing match sticks.