Which source would provide the most bias-free information about second hand smoke as a trigger of asthma?

Question

a brochure from the respiratory information council at Johns Hopkins University

a pamphlet from a tobacco company about the dangers of secondhand smoke

an advertisement by an air-purifying systems corporation

an editorial by an asthma sufferer pushing for a ban on public smoking

Answer 1

The source that would provide the most bias-free information about secondhand smoke as a trigger of asthma would be a brochure from the respiratory information council at Johns Hopkins University.