Which of the following substances can deplete the Earth's ozone layer?

Perfluorocarbons are indeed substances that have been identified as contributors to the depletion of the Earth's ozone layer. These compounds, which are used in various industrial applications, have a stable structure that allows them to persist in the atmosphere for a long time. When they eventually break down, particularly in the stratosphere, they can release chlorine and fluorine atoms. These halogen atoms are highly reactive with ozone molecules, leading to the breakdown of ozone and contributing to the thinning of the ozone layer, a crucial protective barrier against harmful UV radiation.

In contrast, substances like carbon dioxide, methane, and nitrogen do not have a direct, detrimental effect on the ozone layer. Carbon dioxide is primarily known for its role as a greenhouse gas rather than an ozone-depleting substance. Methane can contribute to climate change and may indirectly affect ozone levels, but it doesn't directly deplete the ozone layer itself. Nitrogen, being a major component of the atmosphere, is not involved in ozone depletion. Thus, perfluorocarbons are the correct choice because of their chemical properties that lead to ozone degradation.