Your company has the following architecture for its application on AWS.
A set of EC2 Instances hosting the web part of the application.
A relational database for the backend using AWS RDS
A Load balancer for distribution of traffic
A NAT gateway for routing traffic from the database server to the Internet.
Which of the following can be used to increase the scalability and availability of the application? Choose two answers from the options given below.

Answer options:

A.Launch the EC2 Instances as part of an Autoscaling Group.
B.Enable Multi-AZ for the database.
C.Use a NAT Instance instead of a NAT gateway.
D.Use Route 53 instead of the Load balancer.

Correct Answer: A and B
The AWS Documentation mentions the following.
Amazon EC2 Auto Scaling helps you ensure that you have the correct number of Amazon EC2 instances available to handle your application load. You create collections of EC2 instances, called Auto Scaling groups. You can specify the minimum number of instances in each Auto Scaling group, and Amazon EC2 Auto Scaling ensures that your group never goes below this size. You can specify the maximum number of instances in each Auto Scaling group, and Amazon EC2 Auto Scaling ensures that your group never goes above this size.
Amazon RDS Multi-AZ deployments provide enhanced availability and durability for Database (DB) Instances, making them a natural fit for production database workloads. When you provision a Multi-AZ DB Instance, Amazon RDS automatically creates a primary DB Instance and synchronously replicates it to a standby instance in a different Availability Zone (AZ). 
Option C is incorrect since the NAT gateway is preferred for better scalability and availability.
Option D is incorrect since the Load balancer should be used for distributing traffic.
For more information on EC2 Autoscaling and RDS Multi-AZ, please refer to the below URLs-
https://docs.aws.amazon.com/autoscaling/ec2/userguide/what-is-amazon-ec2-auto-scaling.html
https://aws.amazon.com/rds/details/multi-az/