Which of the Following Statements Regarding IS-IS Route Leaking Are

Which of the following statements regarding IS-IS route leaking are true?

A) IS-IS route leaking can be configured in IPv6 environments.
B) In IS-IS route leaking, the routes to be leaked cannot be summary routes.
C) IS-IS route leaking will not cause neighbor flapping.
D) IS-IS route is used to prevent route loops.
E) IS-IS route leaking can be configured on Level-1 routers.