Which refrigerant is listed under the Kyoto Protocol?

The correct choice is R134a, which was included in the Kyoto Protocol due to its global warming potential. The Kyoto Protocol is an international treaty aimed at reducing greenhouse gas emissions, and it recognizes several substances that contribute to climate change. R134a, a hydrofluorocarbon (HFC), was widely used as a refrigerant but has a significant environmental impact because of its high global warming potential.

While other refrigerants like R22, R410A, and R404A also have their own environmental concerns, R134a was specifically mentioned in discussions around the need to phase out or regulate high-GWP substances. This makes it critical for technicians and engineers to be aware of the implications of using such refrigerants in their practices.