Explanation:

- Option 1: Chlorine

- Chlorine is not one of the six pollutants under the Kyoto Protocol. It is not a greenhouse gas but is known for its role in the depletion of the ozone layer.

- Option 2: Phosgene

- Phosgene is a toxic chemical but is not part of the Kyoto Protocol pollutants. It is primarily known as a chemical warfare agent.

- Option 3: Carbon monoxide

- Carbon monoxide is a harmful air pollutant but not classified under Kyoto Protocol’s greenhouse gases. It contributes to air pollution but not directly to global warming as per Kyoto’s focus.

- Option 4: Perfluorocarbons

- Perfluorocarbons (PFCs) are included under the Kyoto Protocol as they are potent greenhouse gases with a high global warming potential.

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