The correct answer is C, Amazon Route 53. Amazon Route 53 is a scalable Domain Name System (DNS) web service that provides highly available and scalable DNS, domain name registration, and health-checking web services. It allows developers and businesses to route end users to Internet applications by translating domain names into numeric IP addresses. Importantly, Route 53 can be combined with health-checking services to route traffic to healthy endpoints or to independently monitor and/or alarm on endpoints. This makes it the ideal service for setting up a DNS record with a failover routing policy based on health checks, as it can monitor the health of an application's resources and automatically direct traffic to healthy resources while avoiding unhealthy ones.