Your company has just set up a new document server on its AWS VPC, and it has four very important clients that it wants to give access to. These clients also have VPCs on AWS, and it is through these VPCs, they will be given access to the document server. In addition, each of the clients should not have access to any of the other clients` VPCs. Choose the correct answer from the options below.

Answer options:

A.Set up VPC peering between your company`s VPC and each of the clients` VPCs.
B.Set up VPC peering between your company`s VPC and each of the clients` VPCs, but block the IPs from CIDR of the clients` VPCs to deny access between each other.
C.Set up VPC peering between your company`s VPC and each of the clients` VPC. Each client should have VPC peering set up between each other to speed up access time.
D.Set up all the VPCs with the same CIDR but have your company`s VPC as a centralized VPC.

Answer – A
In this scenario, you are asked how resources from 4 VPCs can access resources from another VPC. This is a use case of "Star-Shaped" VPC peering shown in the image below. In this configuration, VPCs that have non-overlapping CIDR with your VPC, are peered for the intent of accessing the resources using their private IP addresses.
Option A is CORRECT because, as mentioned above, the peered VPCs can share and access the resources within each other via their private IP addresses.
Option B is incorrect because you do not need to block any IP addresses in this scenario.
Option C is incorrect because the peering among the client VPCs is unnecessary. The only peering that is needed is between each client and your VPC.Option D is incorrect because, for VPC Peering, the VPCs should not have overlapping CIDRs. So, VPCs having the same CIDR cannot peer.
For more information on VPC Peering, please see the below link
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-peering.html
Note:
The scenario in question is describing an architecture similar to the one given below.
VPC A is your company and the rest of the other 6 companies are your clients and you have set up separate VPC peering connection with each of your clients, allowing only them to have communication with your company VPC. 
VPC D can communicate with VPC A. VPC B can communicate with VPC A in the above configuration. But VPC D cannot communicate with VPC B through VPC peering connection.