Viral marketing refers to a marketing method in which the initiator sends the initial information of the product to the user, and then relies on the user's spontaneous word-of-mouth publicity. This strategy is like a virus, using rapid replication to spread the information to thousands. And even millions of audiences. According to the above definitions, Which of the following are viral marketing:. ["A company encourages them to sell the company's products to more people by developing customers as a sales channel.", 'An enterprise holds an advertising creative design contest to allow consumers to design advertisements for related products.', 'A company randomly sends product advertisements via e-mail and informs that forwarding the advertisement can participate in the lottery.', 'A merchant promoted with a unique advertising word, and netizens reposted it to quickly become a buzzword.']