Which of the following is the responsibility of the customer in the cloud (VM services)?

Answer options:

A.Maintaining the underlying physical servers
B.Security of data hosted on Azure virtual machines
C.Uptime of the Virtual Machine service
D.Cooling in the data center

Answer : B 
The security of the data hosted on the Azure virtual machines. All of the other aspects are the responsibility of Azure. 
For more information on the Shared Responsibility Model, please visit the below URL 

https://docs.microsoft.com/en-us/azure/security/fundamentals/shared-responsibility