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 Virtual Machines that should be used to host the application?

Answer options:

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

Answer – B 

SLA for Virtual Machines : 
Last updated: July 2020 For all Virtual Machines that have two or more instances deployed across two or more Availability Zones in the same Azure region, we guarantee you will have Virtual Machine Connectivity to at least one instance at least 99.99% of the time.
For all Virtual Machines that have two or more instances deployed in the same Availability Set or in the same Dedicated Host Group, we guarantee you will have Virtual Machine Connectivity to at least one instance at least 99.95% of the time.
For any Single Instance Virtual Machine using Premium SSD or Ultra Disk for all Operating System Disks and Data Disks, we guarantee you will have a Virtual Machine Connectivity of at least 99.9%.
For any Single Instance Virtual Machine using Standard SSD Managed Disks for Operating System Disk and Data Disks, we guarantee you will have a Virtual Machine Connectivity of at least 99.5%.
For any Single Instance Virtual Machine using Standard HDD Managed Disks for Operating System Disks and Data Disks, we guarantee you will have a Virtual Machine Connectivity of at least 95%.
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. 
Please refer to the below notes as per the Microsoft official document. 

http://Please refer the below notes as per the Microsoft official document. https://azure.microsoft.com/en-us/support/legal/sla/virtual-machines/v1_9/