Explanation

According to the AWS Shared Responsibility Model:

Customer Responsibilities ("Security IN the Cloud"):

• B. Patch the guest operating system - The customer is responsible for patching and maintaining the operating system running on their EC2 instances
• C. Configure a security group on deployed EC2 instances - Security groups are network-level security controls that customers must configure

AWS Responsibilities ("Security OF the Cloud"):

• A. Maintain the network infrastructure - AWS manages the underlying network infrastructure
• D. Provide physical security for the underlying hardware - AWS provides physical security for data centers and hardware
• E. Manage the underlying hypervisor - AWS manages the virtualization layer (Xen, Nitro, etc.)

The shared responsibility model divides security responsibilities where AWS secures the cloud infrastructure, while customers secure what they put in the cloud, including their data, applications, operating systems, and network traffic configuration.