The correct answer is A) Always preview your document or print a test page first to ensure the margins are not too narrow.
The step to ensure that the page margins are not too narrow is "Always preview your document or print a test page first to ensure the margins are not too narrow."
When you are working on a document that is considerable lenghty, you better preview it to check if it has the correct margins. By printing it you will have a clearer idea of how it looks in reality before delivering your work. The idea is that you be sure that the formatting of the document is appropriate and ready to go.
The other options of the question were B) zoom out your document to ascertain how close to the edges of the document your text is. C) you do not have to ensure that margins are correct, Word will warn you if they are not. D) in the Page Set up dialogue box, ensure that margins are not set to less than 1" for top, bottom, left, and right areas.