The main objective of the Vienna Convention and Montreal Protocol is the protection of the ozone layer.

Option 1: Combat desertification - The Vienna Convention and Montreal Protocol do not specifically address combatting desertification. Desertification refers to the degradation of land in arid, semi-arid, and dry sub-humid areas, usually caused by human activities and climate change.

Option 2: Formulate sustainable developmental goals - While sustainable development is a key principle in environmental agreements, the main objective of the Vienna Convention and Montreal Protocol is specifically focused on addressing the depletion of the ozone layer.

Option 3: Protection of the ozone layer - This is the correct answer. The Vienna Convention was signed in 1985 to provide a framework for international cooperation to protect the ozone layer. The Montreal Protocol was adopted in 1987 to follow up on the Vienna Convention and establish regulations to phase out the production and use of ozone-depleting substances.

Option 4: Combat climate change - While the Vienna Convention and Montreal Protocol indirectly contribute to mitigating climate change by reducing the emissions of ozone-depleting substances (some of which are also greenhouse gases), their main objective is the protection of the ozone layer, not combatting climate change.

In summary, the main objective of the Vienna