An outsider needs access to a resource hosted on your extranet. The outsider is a stranger to you, but one of your largest distributors vouches for him. If you allow him access to the resource, this is known as implementing what?

C. Trusted third party

Explanation:

(TTP) trusted third party is an agent which facilitates interactions between two parties, both of which trust third parties; the third party checks all essential transaction communications between the parties on the basis of the facility to produce fraudulent digital content.