A company is designing a web application that will run on Amazon EC2 instances.

 The correct answers are A and C because Amazon EC2 Auto Scaling and resources that are distributed across multiple Availability Zones are AWS services and features that will improve availability and reduce the impact of failures for the web application. Amazon EC2 Auto Scaling is a service that enables users to automatically adjust the number of Amazon EC2 instances in response to changes in demand or performance. Amazon EC2 Auto Scaling helps users to maintain optimal availability and performance of their applications by adding or removing instances as needed. Resources that are distributed across multiple Availability Zones are AWS features that enable users to increase the fault tolerance and resilience of their applications. Availability Zones are isolated locations within an AWS Region that have independent power, cooling, and networking. Users can launch their resources, such as Amazon EC2 instances, in multiple Availability Zones to protect their applications from the failure of a single location. The other options are incorrect because they are not AWS services and features that will improve availability and reduce the impact of failures for the web application. VPC subnet ACLs are AWS features that enable users to control the inbound and outbound traffic to and from their subnets within a VPC. VPC subnet ACLs do not check the health of a service, but rather filter the network traffic based on rules. Configuration of AWS Server Migration Service (AWS SMS) is an AWS service that enables users to migrate their on-premises servers to AWS. Configuration of AWS SMS does not help to move the Amazon EC2 instances to a different AWS Region, but rather to migrate the servers from the source environment to AWS. Resources that are distributed across multiple AWS points of presence are AWS features that enable users to deliver content to their end users with low latency and high performance. AWS points of presence are edge locations that are part of the AWS Global Infrastructure. Users can use services such as Amazon CloudFront and AWS Global Accelerator to distribute their content across multiple AWS points of presence. Reference: Amazon EC2 Auto Scaling, [Regions, Availability Zones, and Local Zones]