How are routing protocol context implemented in OSPF?

A.
Each routing context is implemented by redistributing into MBGP.

B.
Each routing context is implemented by assigning it to an interface.

C.
Each routing context is implemented as a separate routing process.

D.
Each routing context is implemented as a separate isolated instance of the same routing protocol.

Explanation:

According to the "Implementing Cisco MPLS" Student Guide (Text Part Number:
97-1154-01) Volume 2, version 1.0, page 8-6.
-Routing context=routing protocol run in one vrf
-Routing contexts were introduced in Cisco IOS software to support the need for separate isolated copies of VPN routing protocols. They can be implemented as separate routing processes (OSPF), similar to traditional Cisco IOS software implementation, or as separate isolated instances of the same routing protocol (EBGP, RIPv2).