Which of the Following Best Describes a Social Engagement Ad

Which of the following best describes a social engagement ad?

A) Contains ad (creative image and text) ,along with an option to encourage the viewer to engage with the brand.
B) Includes ad creative,an engagement device,and personalized referral content from people in the viewer's network.
C) Is shared on a person's activity stream following a brand interaction (such as liking the brand) .
D) Motivates the receiver to get involved with the message and help spread it to others.
E) Occurs when an opinion leader publishes brand-relevant content,such as a blog post in social media.