Which of the following statements about VPC and IP addressing is false.

Answer options:

A.You can enable IPv6 support for your VPC and resources
B.You cannot disable IPv4 support for your VPC
C.You can only operate VPC’s in only one mode at a time , either IPv4 or IPv6
D.The default IP addressing for Amazon VPC and Amazon EC2 is IPv4

Answer - C
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.
You cannot disable IPv4 support for your VPC and subnets; this is the default IP addressing system for Amazon VPC and Amazon EC2.
For more information on VPC and IP addressing , please visit the below URL:
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-migrate-ipv6.html