Read the passage from “I can make you rich!” How does the authors use of the phrase “what everyone already knows” affect the tone of the essay ?

a: it suggests that the books are reliable and gives the passage a serious tone.
b: it implies that the books are irresponsible and gives the passage a trustworthy tone .
c: it suggests that the books are well researched and gives the passage a respectful tone .
d: it implies that the books are unoriginal and gives the passage a mocking tone .