Explanation

Security Groups (Option A) and Network Access Control Lists (Option C) are the correct answers for protecting EC2 instances in AWS.

Security Groups:

• Act as virtual firewalls for EC2 instances
• Control inbound and outbound traffic at the instance level
• Stateful - return traffic is automatically allowed regardless of rules
• Operate at the instance level

Network Access Control Lists (NACLs):

• Provide an additional layer of security at the subnet level
• Act as stateless firewalls for controlling traffic in and out of subnets
• Evaluate traffic before it reaches instances
• Can be used to create deny rules

Why other options are incorrect:

• Option B (AMIs): Amazon Machine Images are templates for EC2 instances, not security mechanisms
• Option D (Internet Gateway): This enables internet connectivity for VPCs but doesn't provide security protection

Both Security Groups and NACLs work together to provide defense-in-depth security for EC2 instances in AWS.