Which research question on the topic of air pollution is open-ended and complex? How many people believe that air pollution should be heavily regulated?
Which substances account for the greatest amount of air pollution?
How does air pollution affect human health in the United States?
Which counties in the United States experience the most air pollution?

"How does the air pollution affect human health in the US?"

Explanation:

"How many people believe that air pollution should be regulated?",

"Which substances account for the greatest amount of air pollution?",

and "Which counties in the US experience the most air pollution?"

all have a definite answer. "How does the air pollution affect human health in the US?", however asks what you think about the question and does not have a definite answer.

fisting                       dh dfh dfh d fhd f he   hhb sbh s di penis