Answer:
I feel as B would be correct as the others seem very easy to answer
A. Why is it important to know the effects of air pollution on people living in various cities all over the world? This could be answered by the internet very quickly. it's topic easliy answer, it's pretty much information many know of. Since air population can green house effect which makes heat trapped in the atmostphere and causing enviroments to be destroyed, ice being melted which is one an enviroment destroying the ecosystem causeing sudden fires. ( Because the heat made a place dried out to much and so dry it caught on fire. Very easliy answer, kinda common knowledge.
C. What percentage of Americans think that the effects of air pollution are significant? You can legit look this up and find the percentage, and that it to. It's not feesable, nothing else you could find in this.
D. Why is it important for people to understand air pollution? This is a weaker veriosn of possible answer A. nothing else to explain on this one
E. Why should people care about the effects of air pollution on the environment they live in today? It's like another veriso but better then D but A is still superior
Then B
B is like E and D and A all together and more simple, leading to lots of writing, so can conclude to a strong research question, with lots to answer then just one. Sorta has a little bit of C, but with out the percentage also, and what americans think.