About the definition of router roles within or between OSPF areas, which is correct? (Multiple Choice)

About the definition of router roles within or between OSPF areas, which is correct? (Multiple Choice)
A . Internal router: refers to the router whose all interfaces belong to the same area.
B . ABR: A router that connects one or more areas and connects to the backbone area. These routers act as routing gateways for inter-domain communication.
C . Backbone router: refers to a router that has at least two interfaces that belong to the backbone area.
D . ASBR: It can be an internal router, a backbone router, or a regional edge router.

Answer: ABD