With which router or routers must PE-2 establish an address-family IPv4 BGP neighbor relationship?

In the diagram, the Internet is accessed through a dedicated Internet VPN. With which router or routers must PE-2 establish an address-family IPv4 BGP neighbor relationship?

A.
CE-2

B.
PE-1

C.
PE-IG

D.
PE-1 and PE-IG

E.
CE-1, PE-1 and PE-IG

F.
CE-1, CE-2, PE-1 and PE-IG