Your company has an Azure DevOps project and an Azure subscription. Currently, a pipeline is in place that deploys an application to a virtual machine scale set. The scale set sits behind an Azure Standard Load Balancer. The application is accessed via HTTPS only. You need to implement a solution for implementing a health check for the application. This is based on the following requirements. Be able to identify whether individual instances in the scale set are eligible for an upgrade operation.
It should also minimize administrative effort.
Which of the following would you implement for this requirement?

Answer options:

A.A Custom Script Extension
B.An Application Health Extension
C.Azure Monitor scaling
D.An Azure Load Balancer health probe

Answer – B 
This can be achieved by using the Application Health extension. The Health extension can actually view and monitor the health of your underlying instances. And then automatically it also performs the required upgrades on your instances. 
Option A is incorrect since this can only install custom scripts on the virtual machine. 
Option C is incorrect since this is only a monitoring aspect. 
Option D is incorrect since this is only used to monitor the health of the underlying instances sitting behind the load balancer. 
For more information on the Application Health extension, you can refer to the below link- 

https://docs.microsoft.com/en-us/azure/virtual-machine-scale-sets/virtual-machine-scale-sets-health-extension