Which of the Following Statements Is True About Facebook

Which of the following statements is true about Facebook?

A) Facebook is second to Twitter in the number of registered users.
B) Facebook has remained a "closed system," which means outside search engines such as Google or Bing cannot catalogue information about a particular brand or topic.
C) Facebook is the social media website where users upload more videos to its site than any other site.
D) Facebook's official smartphone app uses location-based technology so users can "check-in" to local businesses to receive targeted promotional offers.