What should you do?

You manage an application that has a front-end tier, a middle tier, and a back-end tier. Each tier is located on a different subnet.
You need to apply access to and between the tiers as follows:
• Only the front-end tier must be able to access the Internet.
• You must permit network access between the front-end tier and the middle tier.
• You must permit network access between the middle tier and the back-end tier.
You must prevent all other network traffic.
You need to apply this configuration to all virtual machines inside the subnets.
What should you do?
A. Use a Network Security Group (NSG).
B. Add a VPN gateway.
C. Add a regional VNET.
D. Add an Availability Set.