(An endpoint is not responding to a request based on the failure threshold provided.

When Amazon Route 53 determines an endpoint is unhealthy based on a failure threshold (e.g., via health checks), it terminates the connection attempt to that endpoint and routes traffic to a healthy alternative, if available. This behavior ensures high availability using routing policies like failover or latency-based routing. The WGU Cloud Deployment and Operations Study Guide (Section 3.1, Route 53 Health Checks) states, "Route 53 stops routing traffic to an unhealthy endpoint by terminating connection attempts once the health check failure threshold is exceeded, redirecting to a healthy resource." Options A, C, and D are not direct actions taken by Route 53 in this scenario.