Which detail best answer the research question "are smokefree policies effective in protecting people from the dangers of secondhand smoke? ”

if you're using E2020 like me the answer would be

D) "SHS from units or common areas where smoking occurs can seep into smokefree units.”

The answer is "SHS from units or common areas where smoking occurs can seep into smokefree units."

Explanation:

It is believed that eliminating smoking in indoor spaces fully protects nonsmokers from exposure to secondhand smoke (SHS) and that a aalf of the US population is covered by state or local smokefree laws that do not allow indoor smoking in worksites and public places, including restaurants and bars. Most people have adopted smokefree rules in their home.

However, exposure in the home remains a significant problem. i.e. secondhand smoke can spread to other units.