D) To determine which posts from a particular user have received the greatest number of comments
Explanation:
Since social media excepting comments from end user website or social media should keep track of end user information such as name with email address and phone extra.
If we do so we can end user information in cans, end user post, wrong post information can be blocked or given end user information for further analysis. Moreover web site can receive positive or negative posts.
For me all four will be my answer. If we don’t track any information about end user it is against to law.