You have a set of EC2 Instances hosted on the AWS Cloud. The EC2 Instances are hosting a web application. Which of the following acts as a firewall to your VPC and the instances in it? Choose 2 answers from the options given below.

Answer options:

A.Usage of Security Groups
B.Usage of AWS Config
C.Usage of Network Access Control Lists
D.Usage of the Internet gateway

Answer – A and C
The AWS Documentation mentions the following.
A security group acts as a virtual firewall for your instance to control inbound and outbound traffic.
A network access control list (ACL) is an optional layer of security for your VPC that acts as a firewall for controlling traffic in and out of one or more subnets. 
For more information on Security Groups, please refer to the following link:
https://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_SecurityGroups.html
For more information on Network Access Control Lists, please refer to the following link:
https://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_ACLs.html