Question

1. what is the biggest source of air pollution?

power plants
agriculture
industry
motor vehicles

Explanation:

To determine the biggest source of air pollution, we analyze the options: Power plants emit pollutants but not the largest. Agriculture contributes to pollution (e.g., ammonia) but less than motor vehicles. Industry has emissions, but motor vehicles (cars, trucks, etc.) are a major source, especially in urban areas, releasing pollutants like CO, NOx, and particulate matter.

Answer:

D. motor vehicles (assuming the fourth option is labeled D; if the original labels were different, adjust accordingly, but based on typical such questions, motor vehicles are the biggest source among these options)