Which Single Sign-On deployment mode should an administrator use for two 5.x vCenter Servers configured with linked mode?

Which Single Sign-On deployment mode should an administrator use for two 5.x vCenter
Servers configured with linked mode?

A.
Basic Single Sign-On with vCenter Server Heartbeat

B.
Multisite Single Sign-On

C.
Basic Single Sign-On

D.
Single Sign-On with Linked Mode