Question:  This is the unpaid peer-to-peer communication of often provocative content originating from an identified sponsor using the Internet to persuade or influence an audience to pass along the content to others:
A: Viral marketing.
B: Word-of-mouth marketing.
C: Direct-response advertising.
D: Peer-to-peer marketing.
Please eliminate two incorrect options first, then think it step by step and choose the most proper one option.