Your company has 200 users. You plan to upgrade all the users from Microsoft Skype for Business Online to Microsoft Teams. Phone System with Teams must be enabled for all users. You need to recommend a coexistence mode for the Microsoft Teams upgrade policy. Which mode should you recommend? 

Answer options:

A. Skype for Business with Teams collaboration
B. Islands
C. Teams only
D. Skype for Business with Teams collaboration and meetings

C

Reference: https://docs.microsoft.com/en-us/microsoftteams/cloud-voice-landing-page