This question needs updating:
You are building an application hosted on AWS for a customer. The customer has a very old firewall that can only whitelist external destinations via IP address only. Which type of elastic load balancer should you use?
The correct answer you were looking for was an NLB, but ALBs also now support static IPs:
Ah, thanks Davetbo. I wouldn’t call the Lambda/NLB evidince that ALB "supports" static IP as it’s a pretty complex solution. However, Global Accelerator can do the job. I’ll update the question to test on knowledge of using EIP with NLB/ALB as well.