Which of the Following Is a Challenge of Marketing Through

Which of the following is a challenge of marketing through social media?

A) Existing social media are resistant to direct advertising.
B) Users may resent an intrusive marketing message.
C) It is hard to measure how frequently social media are used and by how many participants.
D) Most existing social media are already controlled by major corporations.
E) Fewer consumers are using social media such as Facebook and Twitter.