Within a Transit AS, when is it necessary to redistribute the connected interface into IGP at the edge routers?

A.
When synchronization is enabled.

B.
When the edge router is a route reflector.

C.
When the edge routers are redistributed the BGP into IGP.

D.
When the edge routers are not using the next-hop-self option.

E.
When the edge routers are not using loopback interface to establish the IBGP sessions.

Explanation:
When not using the next-hop-self option the next hop is the address of the EBGP peer. The routing table must have a route to the next-hop or the route is not considered. By redistributing connected into the IGP insures that you can get to the next hop neighbor.
Wrong Answer
1. A Synchronization ensures that the routes of the EGP match the IGP.
2. B this has no bearing
3. C Generally this is insane
4. E You still need to be sure that you have a route back to the loopback interface