What is the minimum number of NSGs you should create?

You have an Azure subscription that contains a virtual network named VNET1. VNET1 contains the subnets shown in the following table.

Each virtual machine uses a static IP address.
You need to create network security groups (NSGs) to meet following requirements:
Allow web requests from the internet to VM3, VM4, VM5, and VM6.
Allow all connections between VM1 and VM2.
Allow Remote Desktop connections to VM1.
Prevent all other network traffic to VNET1.
What is the minimum number of NSGs you should create?
A. 1
B. 3
C. 4
D. 12