Your application is hosted in an EC2 instance behind an application load balancer. The SSL traffic is terminated at the load balancer. A certificate for the domain name www.example1.com was requested from AWS Certificate Manager (ACM) and installed in the ALB listener.
Now the application needs to use another certificate to handle a different domain (www.example2.com). 
Which of the following options is the easiest solution to install the certificate?

Answer options:

A.Create another application load balancer, request the second certificate from ACM and install it at its listener.
B.Install the second certificate (www.example2.com) at the same application load balancer with Smart Selection Using SNI.
C.Delete the first certificate from the elastic load balancer and remove the SSL termination at the ELB. Install both certificates on the EC2 instance.
D.Configure an NGINX server on the EC2 instance and install both certificates. Replace the certificate in the ELB with a new certificate and terminate the SSL traffic at ELB.

Answer: B
Option A is incorrect because, with this method, you have to maintain another set of application load balancers and target groups. You may also need to adjust your automation scripts, such as CloudFormation templates to maintain such changes on your AWS infrastructure.
Option B is CORRECT because the second certificate can be installed directly on the ALBlistener, and you can bind up to 25 certificates per load balancer. You can now host multiple TLS secured applications, each with its own TLS certificate, behind a single load balancer. In order to use SNI, all you need to do is to bind multiple certificates to the same secure listener on your load balancer. ALB will automatically choose the optimal TLS certificate for each client.
Option C is incorrect because there is no need to remove the first certificate from the ELB, and the SSL traffic should still be terminated at ALB.Option D is incorrect because it requires additional configurations in NGINX on the EC2 instance to achieve the requirements.
Reference:
https://aws.amazon.com/blogs/aws/new-application-load-balancer-sni/.