A customer relationship management (CRM) application runs on Amazon EC2 instances in multiple Availability Zones behind an Application Load Balancer.

If one of these instances fails, what occurs?

1. The load balancer will stop sending requests to the failed instance.
2. The load balancer will terminate the failed instance.
3. The load balancer will automatically replace the failed instance.
4. The load balancer will return 504 Gateway Timeout errors until the instance is replaced.