An ozone-depleting substance mainly used in:I. Burning fossil fuelsII. ChimneysIII. All human activitiesIV.Cooling and refrigeration applications, and in the manufacture of foam products.

The ozone-depleting substance you're referring to is mainly used in cooling and refrigeration applications, and in the manufacture of foam products. This substance is known as Chlorofluorocarbons (CFCs).

Here's a step-by-step breakdown:

I. Burning fossil fuels: This process primarily releases carbon dioxide (CO2) and other greenhouse gases but not typically ozone-depleting substances.

II. Chimneys: Chimneys are associated with the release of smoke and particulate matter from burning, but not specifically with the release of ozone-depleting substances.

III. All human activities: While it's true that many human activities can contribute to ozone depletion, not all of them do. For example, driving a car that uses gasoline contributes to air pollution, but it doesn't directly cause ozone depletion.

IV. Cooling and refrigeration applications, and in the manufacture of foam products: This is where Chlorofluorocarbons (CFCs) come in. CFCs have been widely used in air conditioning systems, refrigerators, and the manufacture of foam products. They are potent ozone-depleting substances. When released into the atmosphere, they can deplete the ozone layer significantly.