Which of the following statements about use-case testing are most accurate?

Use-case testing involves scenarios based on the use cases of a system. In a use-case diagram, an actor represents a type of user (i). A use-case describes interactions between actors and the system (iii). Test cases can be based on use-case scenarios (v), and use-case testing often identifies gaps not found by testing individual components (vi). However, an actor is not always a human user (iv), and use-cases are not the most common test basis for unit testing (ii).