Which of the following refrigerants which may be found aboard ship is designated as an ozone-depleting substance as defined in the Montreal Protocol on Substances that Deplete the Ozone Layer and is controlled as a result?

Correct Answer: Option A — R-12

R-12, a chlorofluorocarbon (CFC), is strictly controlled under the Montreal Protocol due to its significant ozone-depleting potential. Modern maritime refrigeration systems have transitioned to hydrofluorocarbons (HFCs) like R-134a or R-404A, which do not contain chlorine and therefore do not contribute to the depletion of the stratospheric ozone layer.