What is the reason for this issue?

Refer to the exhibit.

An engineer is trying to redistribute OSPF to BGP, but not all of the routes are redistributed .

What is the reason for this issue?
A . By default, only internal routes and external type 1 routes are redistributed into BGP
B . Only classful networks are redistributed from OSPF to BGP
C . BGP convergence is slow, so the route will eventually be present in the BGP table
D . By default, only internal OSPF routes are redistributed into BGP

Answer: D

Explanation:

If you configure the redistribution of OSPF into BGP without keywords, only OSPF intra-area and inter-area routes are redistributed into BGP, by default.

You can redistribute both internal and external (type-1 & type-2) OSPF routes via this command:

Router(config-router)#redistribute ospf 1 match internal external 1 external 2

Reference: https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/5242-bgp-ospf-redis.html