What should the administrator do first?

MegaCorp is running Smartcenter R70, some Gateways at R65 and some other Gateways
with R60. Management wants to upgrade to the most comprehensive IPv6 support. What
should the administrator do first?

A.
Upgrade R60-Gateways to R65

B.
Upgrade every unit directly to R77.

C.
Check the ReleaseNotes to verify that every step is supported.

D.
Upgrade Smartcenter to R77 first.