You have been asked to create a VPC network topology for your company. The VPC network must support both internet-facing and intranet applications, accessed only over VPN. Both internet-facing and intranet applications must be able to leverage at least 3 AZs each for high availability. How many subnets must you create within your VPC to accommodate these requirements?

Answer options:

A.2
B.3
C.4
D.6

Correct Answer - D
Since each subnet corresponds to one Availability Zone and you need 3 AZs for both the internet and intranet applications, you will need 6 subnets.
For internet-facing and intranet applications, they should be put at different subnets.
For more information on VPC and subnets, please visit the below URL:
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_Subnets.html