How do I restate the letters in the red

Abig hazard on road paragrph writing

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)

Which secondary effect of advertisement happens when a customer is satisfied by a product and buys it for a second time?