Answer:
A) Interactivity
Explanation:
Interactivity refers to the level of communication between a person, and a another person, or a computer program, through digital means.
In this case, the two communication partners can be either two persons, or a person and a computer, and the level of interactivity os the social media site depends on the degree of acoustic, visual and personal contact. If it is high, then, the social media site has a high degree of interactivity.