which two routers must PE-2 establish a VPNv4 BGP neighbor relationship?

In the diagram, the Internet is accessed through a dedicated Internet VPN implementation. With
which two routers must PE-2 establish a VPNv4 BGP neighbor relationship? (Choose two)

A.
CE-1

B.
CE-2

C.
PE-1

D.
CE-IG

E.
PE-IG