Answer:
The correct answers are "burning gasoline at a refinery", "releasing fumes at a chemical plant" and "emitting particles from a dump truck".
Explanation:
Outdoor air pollution is defined as the presence of pollutants in the ambient air. This type of pollution contrasts with indoor air pollution, which is the presence of pollutants within buildings and structures. Fountains of outdoor air pollution will be all machinery that releases pollutants into the ambient air, such as burning gasoline at a refinery, releasing fumes at a chemical plant and emitting particles from a dump truck.
