A company wants to host an application on a set of Virtual Machines in Multi-AZ mode. The application must be made available 99.99 percent of the time. 
In order to comply with the SLA requirement, what is the minimum number of availability zones that should be used to host the application?

Answer options:

A.1
B.2
C.3
D.4

Answer – B 
The application should be designed in the following way. 

Here you have 2 availability zones and a virtual machine per available zone. If one zone goes down, you still have the other zone available. This is the minimum configuration. 
For more information on Availability zones, please visit the below URL- 

https://docs.microsoft.com/en-us/azure/availability-zones/az-overview