Which of the following is a primary source of volatile organic compounds (VOCs)?

Volatile organic compounds (VOCs) are organic chemicals that have a high vapor pressure at room temperature, which means they easily evaporate into the atmosphere. Gasoline and diesel fuels are primary sources of VOCs because they contain hydrocarbons that release VOCs when burned or evaporated. When these fuels are used, especially in transportation, they emit various aromatic hydrocarbons that contribute to air pollution and the formation of ground-level ozone.

In contrast, water vapor from oceans is not considered a VOC, as it is not an organic compound. Dust from the Earth’s crust is primarily made up of inorganic materials and does not release VOCs. Carbon monoxide, while it is a pollutant associated with combustion processes, is not categorized as a VOC but rather a different class of air pollutant. Therefore, gasoline and diesel fuels are the clear answer when identifying primary sources of VOCs.