A. e-mail is the most common workplace in writing
Quotations add emphasis to ideas, so A is out. If quotations add emphasis to ideas then they also add strong support to claims therefore C is out. Quotations add credibility to writing as well so D is out. Therefore B is the right answer, you would not include direct quotations in a story to add length to a boring story.
Really bad diseases trasnmitted into the body can be insidious with harmful effects.
