Which of the following refrigerants cause the least amount of harm to stratospheric ozone?

HFCs, or hydrofluorocarbons, are designed to have a lower impact on stratospheric ozone compared to other refrigerants like CFCs (chlorofluorocarbons) and HCFCs (hydrochlorofluorocarbons). CFCs and HCFCs contain chlorine, which is known to contribute to ozone depletion when released into the atmosphere. The chlorine atoms can catalytically break down ozone molecules, leading to significant ozone layer damage.

While HFCs do not contain chlorine and thus do not directly harm the ozone layer, it's important to note that they can still have high global warming potential (GWP) and are subject to regulatory challenges aimed at reducing greenhouse gas emissions.

HFOs (hydrofluoroolefins) are also more environmentally friendly than HFCs because they are designed to have a very low GWP and do not pose a risk to the ozone layer. However, in the context of this question focusing on the options provided, HFCs are recognized for causing the least ozone harm among the specific choices of CFCs, HCFCs, and HFOs.