You have created a VPC with CIDR block 10.0.0.0/24, which supports 256 IP addresses. You want to now split this into two subnets, each supporting 128 IP addresses. Can this be done and if so how will the allocation of IP addresses be configured? Choose the correct answer from the options below

Answer options:

A.One subnet will use CIDR block 10.0.0.0/127 (for addresses 10.0.0.0 - 10.0.0.127) and the other will use CIDR block 10.0.0.128/255 (for addresses 10.0.0.128 - 10.0.0.255).
B.One subnet will use CIDR block 10.0.0.0/25 (for addresses 10.0.0.0 - 10.0.0.127) and the other will use CIDR block 10.0.1.0/25 (for addresses 10.0.1.0 - 10.0.1.127).
C.One subnet will use CIDR block 10.0.0.0/25 (for addresses 10.0.0.0 - 10.0.0.127) and the other will use CIDR block 10.0.0.128/25 (for addresses 10.0.0.128 - 10.0.0.255).
D.This is not possible.

Answer – C
This is clearly given in the aws documentation
For more information on VPC and subnets please see the below link:
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_Subnets.html