You currently have a VPC that has a set of Instances. You now have a requirement to host an application in the VPC which primarily communicates on IPv6. What do you need to do to enable this requirement?
Select 2 answers.

Answer options:

A.Disable IPv4 for the subnet.
B.Disable IPv4 for the VPC.C.Enable IPV6 for the subnet.
D.Enable IPV6 for the VPC.

Answer – C and D
The AWS Documentation mentions the following.
If you have an existing VPC that supports IPv4 only, and resources in your subnet that are configured to use IPv4 only, you can enable IPv6 support for your VPC and resources. Your VPC can operate in dual-stack mode — your resources can communicate over IPv4, or IPv6, or both. IPv4 and IPv6 communication are independent of each other.
In order to enable ipv6 on VPC and subnet level, we need to enable manually on VPC and subnet. So, it looks like option C is also the correct answer. 
https://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-migrate-ipv6.html#vpc-migrate-ipv6-cidr
Options A is incorrect since this setting is pertinent to the VPC.Option B is incorrect since you cannot disable IPv4 for the VPC.For more information on using Ipv6, please refer to the below URL
https://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-migrate-ipv6.html