As AWS grows, most of your clients` main concerns seem to be about security, especially when all of their competitors also seem to be using AWS. One of your clients asks you whether having a competitor who hosts their EC2 instances on the same physical host would make it easier for the competitor to hack into the client`s data. Which of the following statements would be the best choice to put your client`s mind at rest?

Answer options:

A.Different instances running on the same physical machine are isolated from each other via a 256- bit Advanced Encryption Standard (AES-256).
B.Different instances running on the same physical machine are isolated from each other via the hypervisor and via a 256-bit Advanced Encryption Standard (AES-256).
C.Different instances running on the same physical machine are isolated from each other via the hypervisor.
D.Different instances running on the same physical machine are isolated from each other via IAM permissions.

Answer - C
Options A and B are incorrect because 256-bit AES is used for encrypting the data. Ensuring the isolation of the VMs running on a hypervisor is not its responsibility. 
Option C is CORRECT because it is the hypervisor that hosts the VMs responsible for ensuring that the VMs are isolated from each other despite being hosted on the same underlying hypervisor.
Option D is incorrect because IAM permissions have nothing to do with the isolation of the VMs running on a hypervisor.
More information on this topic:
The shared responsibility model for infrastructure services, such as Amazon Elastic Compute Cloud (Amazon EC2), for example, specifies that AWS manages the security of the following assets: 
• Facilities 
• Physical security of hardware 
• Network infrastructure 
• Virtualization infrastructure
https://d0.awsstatic.com/whitepapers/aws-security-best-practices.pdf