A User Has Created a VPC with CIDR 20

Multiple Choice

A user has created a VPC with CIDR 20.0.0.0/16. The user has created one subnet with CIDR 20.0.0.0/16 by mistake. The user is trying to create another subnet of CIDR 20.0.0.1/24. How can the user create the second subnet?

A) There is no need to update the subnet as VPC automatically adjusts the CIDR of the first subnet based on the second subnet's CIDR
B) The user can modify the first subnet CIDR from the console
C) It is not possible to create a second subnet as one subnet with the same CIDR as the VPC has been created
D) The user can modify the first subnet CIDR with AWS CLI