Online advertising, which includes search, banner, mobile, and other forms of digital messaging, has recentl nearly $$50$ billion in revenue. Which of the following factors best explains this growth?

A$)$ Online advertising is less expensive than traditional broadcast advertising.

B$)$ Search engines and social media have become powerhouses in the media landscape.

C$)$ Online advertising is easier to create than traditional broadcast advertising.

D$)$ Online advertising allows more direct measurement of return on marketing investment.