Answer: Sticky sessions are enabled for the load balancer, Instances of a specific capacity type aren’t equally distributed across Availability Zones

Sticky sessions are enabled for the load balancer - This can be the reason for potential unequal traffic routing by the load balancer. Sticky sessions are a mechanism to route requests to the same target in a target group. This is useful for servers that maintain state information in order to provide a continuous experience to clients. To use sticky sessions, the clients must support cookies. When a load balancer first receives a request from a client, it routes the request to a target, generates a cookie named AWSALB that encodes information about the selected target, encrypts the cookie, and includes the cookie in the response to the client. The client should include the cookie that it receives in subsequent requests to the load balancer. When the load balancer receives a request from a client that contains the cookie, if sticky sessions are enabled for the target group and the request goes to the same target group, the load balancer detects the cookie and routes the request to the same target. If you use duration-based session stickiness, configure an appropriate cookie expiration time for your specific use case. If you set session stickiness from individual applications, use session cookies instead of persistent cookies where possible. Instances of a specific capacity type aren’t equally distributed across Availability Zones - A Classic Load Balancer with HTTP or HTTPS listeners might route more traffic to higher-capacity instance types. This distribution aims to prevent lower-capacity instance types from having too many outstanding requests. It’s a best practice to use similar instance types and configurations to reduce the likelihood of capacity gaps and traffic imbalances. A traffic imbalance might also occur if you have instances of similar capacities running on different Amazon Machine Images (AMIs). In this scenario, the imbalance of the traffic in favor of higher-capacity instance types is desirable. Incorrect options: There could be short-lived TCP connections between clients and instances - This is an incorrect statement. Long-lived TCP connections between clients and instances can potentially lead to unequal distribution of traffic by the load balancer. Long-lived TCP connections between clients and instances cause uneven traffic load distribution by design. As a result, new instances take longer to reach connection equilibrium. Be sure to check your metrics for long-lived TCP connections that might be causing routing issues in the load balancer. For Application Load Balancers, cross-zone load balancing is disabled by default - This is an incorrect statement. With Application Load Balancers, cross-zone load balancing is always enabled. After you disable an Availability Zone, the targets in that Availability Zone remain registered with the load balancer, thereby receiving random bursts of traffic - This is an incorrect statement. After you disable an Availability Zone, the targets in that Availability Zone remain registered with the load balancer. However, even though they remain registered, the load balancer does not route traffic to them.