What would be the best source for objective, accurate data?

a survey conducted by a university
a blog entry describing the results of the survey
somebody who took the survey

Which statement best explains the function of the subtitlein this text? a.it provides additional information that narrows the focusof the text.b.it draws attention to important information in the table ofcontents.c.it introduces the various sections that appear withineach chapter.d.it explains the author's primary reason for writing aboutthis topic.correct (a)