An application is running on multiple Amazon EC2 instances.

The correct answer is B because Application Load Balancer is an AWS load balancer that will meet the requirements and take the least amount of effort to deploy. Application Load Balancer is a type of Elastic Load Balancing that operates at the application layer (layer 7) of the OSI model and routes requests to targets based on the content of the request. Application Load Balancer supports advanced features, such as path-based routing, host-based routing, and HTTP header-based routing. The other options are incorrect because they are not AWS load balancers that will meet the requirements and take the least amount of effort to deploy. Network Load Balancer is a type of Elastic Load Balancing that operates at the transport layer (layer 4) of the OSI model and routes requests to targets based on the destination IP address and port. Network Load Balancer does not support path-based routing. AWS OpsWorks Load Balancer is not an AWS load balancer, but rather a feature of AWS OpsWorks that enables users to attach an Elastic Load Balancing load balancer to a layer of their stack. Custom Load Balancer on Amazon EC2 is not an AWS load balancer, but rather a user-defined load balancer that runs on an Amazon EC2 instance. Custom Load Balancer on Amazon EC2 requires more effort to deploy and maintain than an AWS load balancer. Reference: Elastic Load Balancing