Answer:
D. informal language
Explanation:
While all the other elements mentioned can help an author create an eefctive paragraph in the body of a research report, informal language is not usually one of these. Informal language can make an author sound unprepared or uninformed, which can damage the author's credibility. Moreover, if the language of a piece is too informal, people might not take it seriously, which would make the text less effective or less persuasive.
