A customer is hosting the company website on a cluster of web servers behind a public-facing Elastic Load Balancer. The customer also uses Amazon Route 53 to manage their public DNS. How should the customer configure the DNS zone apex record to point to the ELB?

Answer options:

A.Create an A record pointing to the IP address of the Load Balancer.
B.Create a CNAME record pointing to the Load Balancer DNS name.
C.Create a CNAME record aliased to the Load Balancer DNS name.
D.Create an alias record that points to your Load Balancer.

Answer – D
Option A is incorrect because it suggests creating a record pointing to the IP address of the ELB; but, ELBs don`t have predefined IP addresses.
Options B and C are incorrect because you should preferably create an ALIAS record rather than a CNAME record. See the "More information..." section for more details.
Option D is CORRECT - To route domain traffic to an Elastic Load Balancer, use Amazon Route 53 to create an alias record that points to your load balancer. An alias record is a Route 53 extension to DNS. It`s similar to a CNAME record, but you can create an alias record for the root domain and subdomains.
Please refer to page 386 in the below link:
https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/route53-dg.pdf
More information on ALIAS Record:
Alias resource record sets are virtual records that work like CNAME records. But they differ from CNAME records in that they are not visible to resolvers. Resolvers only see the A record and the resulting IP address of the target record. Unlike CNAME records, alias resource record sets are available to configure a zone apex (also known as a root domain or naked domain) in a dynamic environment.
For more information on the zone apex, please refer to the link below.
http://docs.aws.amazon.com/govcloud-us/latest/UserGuide/setting-up-route53-zoneapex-elb.html
For more information on choosing between ALIAS and Non-ALIAS records, please refer to the link below.
https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/resource-record-sets-choosing-alias-non-alias.html?console_help=true