Evidence is an essential piece of any quality piece of expository writing in that it
a. supplies the reader with information that corroborates the reader's own beliefs.
b. assures the reader that what the author is saying is undeniably true.
c. establishes the author as an unqualified expert in the field.
d. provides grounds for belief about something.

Expository writing investigates an idea or argument for the purpose of informing or persuading readers. the genre takes many forms, including comparison and contrast, argumentative, analytical and cause and effect essays. you can analyze the effectiveness of an expository work by evaluating its structure, style and use of clear examples and evidence to support its conjectures.