Which two-stage configuration process is correct in Cisco IOS XR Software?

Which two-stage configuration process is correct in Cisco IOS XR Software?

A.
Enter configuration mode, then make configuration changes,

B.
Make configuration changes, then enter "commit" to make configuration changes persist.

C.
Make configuration changes, then enter "copy run start" to make configuration changes persist

D.
Enter admin mode, then make configuration changes.