What is the procedure to upgrade all Cisco SD-WAN devices to a recent version?

What is the procedure to upgrade all Cisco SD-WAN devices to a recent version?
A . The upgrade is performed for a group of WAN Edge devices first to ensure data-plabe availability when other controllers are updated.
B. The upgrade is performed first on vManage, then on WAN Edge devices, then on vBond and finally on vSmart. The reboot must start from WAN Edge devices.
C. Upgrade and reboot are performed first on vManage then on vBond then on vSmart. and finally on the Cisco WAN Edge devices.
D. Upgrade and reboot are performed first on vBond. then on vSmart. and finally on the Cisco WAN Edge devices.

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Answer: C