What Type of Cybermediaries Are Intelligent Agents

What type of cybermediaries are intelligent agents?

A) They are travel agents who answer questions online.
B) They are people who can help computer users with problems they encounter when trying to shop online; contacts are direct and in-person.
C) They are sophisticated software programs that use collaborative filtering technologies to learn from past user behaviour in order to recommend new purchases.
D) They are search engines specifically designed for online marketing and other forms of e-commerce.