On an OSPF network, an IR in area 0 must be a BR, but an...

Comprehensive and Detailed In-Depth Explanation:

Internal Router (IR) : A router that exists entirely within a single OSPF area (e.g., Area 0). It does not have to be a Border Router (BR) .

Area Border Router (ABR) : A router that connects two or more OSPF areas . It maintains separate LSDBs for each area and forwards summary LSAs between them.

Autonomous System Boundary Router (ASBR) : A router that connects the OSPF domain to an external network (e.g., BGP, another OSPF AS).

The statement is false because:

An IR in Area 0 does not have to be a BR (Border Router). It can just be a normal internal router.

An ASBR does not have to be an ABR . An ASBR can exist inside any OSPF area , even a single area, without needing to connect multiple areas.

???? Reference: Huawei HCIA-Datacom Study Guide, OSPF Router Types and Area Concepts.