CFCs are known to be highly reactive in which part of the atmosphere?

Chlorofluorocarbons (CFCs) are primarily known for their reactivity in the stratosphere, rather than the lower levels of the atmosphere. In this context, the correct answer is the upper levels of the atmosphere, particularly the stratosphere, where CFCs undergo photolytic breakdown due to exposure to ultraviolet (UV) radiation. This reaction leads to the release of chlorine atoms, which can then catalyze the destruction of ozone molecules, contributing to ozone depletion.

While the troposphere is where the majority of atmospheric chemical reactions occur, CFCs are relatively stable in this lower region, which is why they persist until they reach the upper atmosphere. In the exosphere, the atmospheric density is extremely low, and the likelihood of CFCs reacting is minimal due to the sparse molecular interactions. Therefore, understanding the behavior of CFCs requires knowledge of their chemical stability and reactivity in different atmospheric layers.