Exam CTFL topic 1 question 27 discussion

Which of the following statements about use-case testing are most accurate?
(i)In a use-case diagram an actor represents a type of user.
(ii)Use-cases are the most common test basis for unit testing.
(iii)A use-case describes interactions between actors.
(iv)An actor is always a human user that interacts with the system.
(v)Test cases can be based on use-case scenarios.
(vi)Use-case testing will often identify gaps not found by testing individual components.