Environmental Protection Agency (EPA) MVAC Certification 2025 – 400 Free Practice Questions to Pass the Exam

The correct choice indicating that CFCs are highly reactive in the lower levels of the atmosphere pertains to the behavior and interactions of these compounds within various atmospheric layers. In the lower levels of the atmosphere, such as the troposphere, CFCs can undergo various chemical reactions, often facilitated by the presence of sunlight and other atmospheric constituents.

While CFCs are relatively stable in the troposphere initially, they eventually break down in the stratosphere due to ultraviolet radiation. However, in the lower atmosphere, reactions can include interaction with hydroxyl radicals, which can lead to processes such as ozone depletion when CFCs are eventually released into the upper layers of the atmosphere after ascending from ground level, but the real focus of high reactivity is highlighted by other pollutants and substances that are present primarily in these lower layers.

Understanding this layered structure of the atmosphere is crucial while noting that while upper levels have limited interaction due to lower particle densities, the exosphere is too far removed from typical atmospheric chemical activities. The reactivity of CFCs, therefore, is greatly influenced by their initial interactions in lower layers, highlighting the importance of atmospheric chemistry and pollution control measures.