You need to remove a host pool that is no longer in use. But when you attempt to delete it, it fails with an error. 
Which of the following actions do you need to perform first before deleting a host pool?

Answer options:

A.Delete RBAC roles associated with the host pool
B.Remove the app groups associated with the host Pool
C.Enable drain mode on all session hosts in the host pool
D.Decrease the Max session limit

Correct Answer: B 
All the host pools created in AVD are attached to app groups and session hosts. You need to delete app groups associated with the host pool before deleting the host pool.
Option A is incorrect. Deleting RBAC roles associated with the host pool is not the necessary step.
Option B is correct. You need to delete app groups associated with the host pool before deleting the host pool.
Option C is incorrect. It is a good practice to put the session hosts in drain mode and wait for the users on the host pool to log off, but it is not a necessary step.
Option D is incorrect. Decreasing the Max session limit is the incorrect option.
Reference: 
To know more about how to delete a host pool, please visit the below-given link: 

https://docs.microsoft.com/en-us/azure/virtual-desktop/delete-host-pool?tabs=azure-portal