Which of the following service is a cloud-based network security service that helps to protect the resources that are stored in an Azure Virtual Network?

Answer options:

A.Azure Sentinel
B.Azure Key Vault
C.Azure Dedicated Hosts
D.Azure Firewall

Answer : D 
The Azure Firewall is a cloud-based service that can be used to protect resources in an Azure virtual network. Here you can define network rules and application rules to protect your Azure Virtual Network.
Option A is incorrect since this is used for threat detection
Option B is incorrect since this is used for storing secrets, encryption keys and certificates
Option C is incorrect since this is used for providing a physical server as a resource
For more information on Azure Firewall, please visit the below URL 

https://docs.microsoft.com/en-us/azure/firewall/overview