Which refrigerant is classified as an HFO?

HFO, or hydrofluoroolefin, refers to a category of refrigerants known for being more environmentally friendly compared to traditional refrigerants. Among the options provided, R-1234ze is classified as an HFO. This refrigerant has a lower Global Warming Potential (GWP) compared to the others listed, which is a significant factor in its usage as industry and regulatory trends shift towards more sustainable options. The characteristics of HFOs include better efficiency and a reduced impact on the ozone layer. This aligns with the goal of minimizing greenhouse gas emissions and addressing climate change.

In contrast, R-22, R-134a, and R-410A are classified as HFCs (hydrofluorocarbons), which, while they do not deplete the ozone layer, still have higher GWP values. Therefore, R-1234ze stands out as the correct answer for being an HFO.