Locate the main idea because that's most important thing
1 filling out forms
Pupils information sheets
3 deposit slip
4 borrowers card
5 B
The most credible source in terms of researching the effects of smoking is letter b, research article in a scientific journal. It is because a credible source means that it is valid or could be relied on in which the research article is, because it has been researched and holds validity of which contains proof. Other choices does not correspond to the question for they don't hold any validity or proof in the topic that could be reliable.
